I'm no authority, but here is what I use.
Why buy one app when you can buy a package deal that works together (maybe)? If I could, I'd still be using WordPerfect 8 for long documents and HTML, but those days are past. I've also placed several writing "environments" in this category.
iLife 09 -- iPhoto doesn't handle editing the way I like, nor do I like it for photo management, but iPhoto is great for making slideshows quickly and greeting cards. The latest Aperture is just as good for slideshows, only failing to make cards and calendars. However for easy access to photos in other Apple apps you really need to use either iPhoto or Aperture for photo management. Happily, now both programs will open the other's databases, so it's now easy to make a card from images stored in Aperture. I use GarageBand for sound track editing. I'd love to create music but I just don't have time to pick up on that hobby again. I'll mention iTunes here. I'm very happy with it, even the new version, and don't miss what I used on my PCs (MusicMatch Jukebox). No longer part of iLife, but it used to be even though it was always freely downloadable from the Apple site. I've basically switched from iMovie to Final Cut Pro X. The applications iWeb and iDVD have been discontinued. I rarely used them, and in fact haven't used them in years. I no longer make video DVDs and use Dreamweaver for my website.
iWork 09 -- Keynote is a great replacement for Powerpoint, Pages is a good word processor and adequate page composition tool for my needs. Numbers has finally moved to acceptable. All three of these create documents that look much more polished than I can make them with Microsoft Office. This is now my primary office suite.
Office 2011 for Mac -- Needed for that imaginary full compatibility with Windows. Otherwise avoid the Microsoft suite! But it is a must have. Comes with the fonts my students have been using but otherwise don't appear on Macs. New "cloud" scheme has shot up the price of the suite. I really hate it!
OpenOffice.org, LibreOffice, NeoOffice -- I've actually settled on LibreOffice and dropped the others, however I still have comments about them! An interesting horserace where one of these is anxious to get "Place" to the winning Microsoft Office. These three are built from the same code base. OpenOffice and LibreOffice are the result of a split in developers, so are likely to diverge. While LibreOffice was favored, OpenOffice had a recent release (under their new ownership, Apache) so the race continues. However OpenOffice seems to have dropped WordPerfect format support. NeoOffice is supposed to be better integrated with OS X, but the author either doesn't understand the reasoning behind the new Lion features or can't figure out how to incorporate them. He did a half-***ed job of it, and the bizarre purchase scheme requires one to pay extra to complain/offer suggestions.
A full suite but seems sluggish and has no templates, so forget its PowerPoint clone. Only use its Word clone for it's ability to import some word files better than Word as well as, thankfully, WordPerfect files. Also it can read OpenOffice files created by my students. It's free (except for NeoOffice), so no reason not to have it except for the disk space.
Scrivener -- A great program for organizing and writing long documents. It's really a writing environment. It has many features to cover all types of writing. If you write anything book length I strongly suggest checking it out
Circus Ponies Notebook -- Terrible name for a program that is fairly equivalent to Microsoft One Note. Great for keeping notes. Seems a bit buggy and sluggish on occasion and commands are confusing. I've used it for work projects, class notes (where it has replaced physical 3-ring notebooks), and for record keeping of Senior Projects. This program probably gets used more than any other I've got.
Coda 2 -- I bought this website editor because it's well regarded. Actually suits my coding style (writing in plain-text my own HTML codes). Much faster than Dreamweaver, and I'm considering moving to this program for my websites. I'm editing this page in Coda 2 now.
Adobe Creative Suite 5 Design Premium -- I previously bought CS3 just for Photoshop, but with the academic pricing I can get, went for the whole suite. I upgraded to version 5 Premium, which has Dreamweaver that I want and some Flash apps I'll probably never use. You can't beat the power of the Adobe apps, but none of them are easy to use. Photoshop is basically a must have for photography, and Dreamweaver is a perfect replacement for an old IBM product I used to use for HTML. Illustrator is overkill for my vector graphics needs, but I've got it if I need it. I wanted to learn InDesign, but decided that it didn't really offer anything for me (although the latest version is good for EPUB, apparently). I expect to buy another copy just before retiring from teaching.
EazyDraw -- All I really want is MacDraw. I ended up with EazyDraw. It does what I want but for my needs does too much which makes it too complicated. Still much better than Adobe Illustrator. OpenOffice has a drawing program that is dreadful, and as far as I'm concerned the drawing capabilities of iWork or Office 2004 in their presentation packages just doesn't hack it.
OmniGraffle -- As EazyDraw is to MacDraw, OmniGraffle is to Visio. By far the easiest way do draw charts (flow charts and state diagrams in my case), but EazyDraw has better drawing tools.
Mathtype -- generates equations that look nice. While a commercial product, it can be used indefinitely for free if you are satisfied with a limited mode that matches the functionality of the OEM versions formerly shipped with Microsoft Office and AppleWorks (but not iWork, for some reason). It's integrated into Pages and Scrivener
AutoDesk SketchBook Pro -- easy to use drawing program that I occasionally use as a "white board" with a projector in class
Screen Marker -- presentation utility for drawing on the screen. I got this from the Mac App Store. I liked OmniDazzle better, but it's no longer supported and stopped working with Lion.
I use Photoshop CS5, Bridge CS5, and iPhoto as mentioned above. Also:
Aperture 3.1 -- I bought this because I had been using 1.5 to access my photos (which are "reference copies" so I can access the same photos with iPhoto or Finder). 1.5 doesn't run under Snow Leopard. 2.1 was supposed to be faster, but I didn't notice any difference. 3.0 became a different story. It now replaces my use of iPhoto, and most of the time Photoshop as well.
Hugin -- A panorama stitcher that is feature rich, confusing, but great results. It's also free.
Nik Plugins -- The Nik suite of plugins does a fantastic job of pulling marginal photos back to life. Perfect when the conditions were not quite right and you don't have an alternative shot. Recently purchased by Google, the suite has had a major drop in price. It integrates with Aperture as well as Adobe software.
Photomatix Pro -- For HDR photography. Hard to beat. I also have the Aperture plug-in.
Huey Pro -- display calibration hardware and software. Doesn't seem to work properly with Mountain Lion so will need to replace.
imageMagick -- command line programs for image manipulation
Final Cut Pro X and Compressor -- I use for my classes, producing 2-4 hours a week during the school year. I used to use iMovie for this, but the multi-cam editing in Final Cut had me change.
iSHowU HD Pro-- video screen capture. I use this all the time. Will capture Parallels Windows screens. Fast operation. Flexible. Low cost.
Perian -- plug in for Quicktime. Handles all common formats not done by Quicktime alone. Free. Also no longer developed, but really doesn't need to be.
VLC Media Player -- plays video formats not handled by QuickTime. Plays DVDs outside of region 1.
Microsoft Silverlight -- needed for viewing some web videos.
Plex -- Media server and player. I use this all over the house.
Handbrake -- format conversion from DVDs for viewing on PCs (without DVD drives) or iPods. I also use it for FLV conversion which doesn't work anymore in VisualHub (outdated codecs?). 64-bit version is very fast.
QuickTime 7 Pro -- upgrade from Apple adds editing and other useful features. Inexpensive. The new QuickTime X is missing most of the QuickTime Pro features, so isn't a substitute. Luckily QT7 Pro is still available and supported.
MPEG Streamclip -- Looks like a possible alternative to using QuickTime 7 Pro and Handbrake for transcoding, but I haven't had much experience with it yet.
XTools -- must have on OS X. Free from Apple. I've never written a Cocoa or Carbon application, but I've used the gcc compiler for command line apps. Yes, there is a command line! This package also provides support for Subversion version control.
Netbeans -- I'm a big fan of Java, and this gives me a good cross-platform development tool. Free. I preferred the old Borland JBuilder, but dropped it after they went to Eclipse. They have also dropped Mac OS X support. I've also been using Netbeans for Qt
Epsilon -- programmer's editor. Comes with Mac (using X11), Linux, and Windows versions. Earlier versions existed for DOS and OS/2. It's been around for many years and I've used it for at least 20. Not cheap, but I couldn't live without it and use it on all the platforms. EMACS without warts. I'm using it to edit this html now.
BBEdit -- A long time contender in the Mac world, I recently bought it thinking of going all native Mac (my favorite Epsilon editor isn't native but uses X11). While it has many strong features, it's missing the ability to do smart indents (and reformatting) of code which every other programmer's editor seems to be able to do. It also doesn't have tags which I've found indispensable. But it does open quickly and I've set it to be my default editor when I click on a C source file. It also looks good for HTML, but I've got Coda and Dreamweaver for that.
We are now using Quicken under Windows in Parallels. The new Quicken for the Mac is woefully inadequate. Sorry Apple, you just don't rate well for this. I've looked at several of the available programs and don't like any of them.
H&R Block TaxCut -- I used it on my PC and now they have a Mac version, so tax time is a bit less taxing.
Mail, Contacts (formerly Address Book), Calendar, Reminders -- Does what I want and elegantly. I hate Outlook at work. Now that I use an iPod Touch as my PIM, it syncs the addresses, notes, and calendar with ease. I used to use a Palm, but syncing was erratic with a Mac and Palm is basically fading away. I used to use Thunderbird for mail, but OS X Mail is much nicer. Part of OS X.
Spotlight -- searches and finds everything. Also provides a quick dictionary and calculator. The feature I miss most when I'm on the windows machine at work. Part of OS X.
Alfred 2 -- considering this as a smarter replacement for Spotlight.
Hazel -- I'm going "paperless" and bought a Fujitsu ScanSnap scanner. Hazel looks into the scanned documents (and statements downloaded from websites where I've gone paperless), renames, dates, and files them into the appropriate archival folder. I also scan receipts both with the ScanSnap and with my iPod Touch's camera (and transfer using DropBox) and Hazel files them away, too, and deletes them after 3 months. It also does housekeeping, cleaning out old Mail Downloads, color tagging the download folder on file age (so I can manually clean out old downloads), and emptying the trash when it starts to smell.
Chronosync -- I use this utility to synchronize data files between my MacBook and my iMac. It has been working flawlessly. Cost feels a little high, but worth it to me.
TimeMachine -- Not so much of a backup tool as it is a version management system. Go back in time to recover an earlier version of a document or some files that you thought you wouldn't need. Not a replacement for true backups.
SuperDuper! -- Stupid name for a robust backup (to external drive) program. I keep backups "off site". I've paid for this to get the fast, synchronizing backup mode.
Safari -- Has become my primary browser because of speed and ease of use. Part of OS X. I use the Click-to-Flash and Ad Block plugins.
Firefox -- alternate browser. I use the Adblock Plus, NoScript, and CustomizeGoogle extensions.
1Password -- excellent password vault.
Dropbox -- shared files across systems, synchronized over Internet.
CrashPlan -- cloud backup service I use for most of my computers. Recent (Jan 2013) major price increase, but still very inexpensive when backing up multiple systems. I've got it backing up 4 computers, over 1 TB.
Forklift -- I got this program at a steep discount, so tried it out. It has for file manipulation so it can replace Finder functionality as well.
Chicken -- VNC client program for accessing Linux screens. Formerly "Chicken of the VNC."
Microsoft Remote Desktop -- remote desktop client for accessing Windows screens.
Skype -- I use this for video conferencing with students who are likewise equiped.
Bonjour for Windows -- allows my Windows systems and virtual machines to print to my Mac-connected printers.
Daily Comics -- widget for Dashboard.
Parallels 6.0 -- I've tried VMWare Fusion but Parallels seems to be better integrated into OS X. Early versions of Parallels were flakey, support has been lackluster, and each interim upgrade a hazard, but they finally have their act together with a smooth running product.
Bartender -- This has nothing to do with beverages but everything to do with tending the Menu Bar at the top of the screen. That row of icons on the right gets so big as to interfere with menu items. Bartender merges the ones you don't want to see all the time into a secondary bar. Probably the most useful utility I've obtained in recent years.
Onyx -- a good way to do system cleanups and set hidden options.
Disk Inventory X -- graphically view disk utilization.
iStat -- widget for DashBoard that shows system status. I use the Nano version on the MacBook and the Pro version on the iMac.
A Better File Rename -- I used to use Renamer4Mac, which was free. I got this one from a MacUpdate bundle. Runs as a service.
Stuffit Expander -- for those increasingly rare Stuffit format archives.
BetterTouchTool -- provides the capability to program additional multi-touch gestures and modify existing gestures in the MacBook touch pad and the new Magic Mouse. Also will snap windows to edges and corners of the screen, like on Windows 7. Particularly dramatic for Magic Mouse users since that mouse has less built-in features than the previous Mighty Mouse. I use the similar BetterSnapTool on my MacBook Pro.
MenuPop -- makes the top menu bar a popup. This is very convenient when working on a second display in a multiple monitor setup or on a single large display. Useful on my iMac which has a second display. Works from keyboard, which is also a plus.
QUICKSILVER -- I don't use this anymore, instead relying on SpotLight as my program launcher. I never got into the advanced features of this program. I've also tried and rejected Alfred.
Encyclopedia Britannica -- Wikipedia is free and surprisingly faster to use. Of course Wikipedia isn't authoritative and I haven't removed the Encyclopedia, but I don't use it any more.
Coconut Battery -- A free utility to display everything you want to know about your battery. But I've discovered all that information is available anyway.
DockStar -- shows count of unread messages in different categories on the dock. This should have been built-in the Mail program. However I decided it wasn't really necessary.
Calico -- a panorama stitcher that is easy to use but has few controls -- either it does the job or it fails miserably with no recourse. I just think Hugin is better because it handles the tricky situations that keep coming up.
Stomp -- format conversion (transcoding). I got a good deal with this when I bought iShow U Pro, but it isn't reliable and I mostly use Handbrake now.
Cyberduck -- A nice FTP/SCP program but I've switched to using ForkLift.