I just went through the same thing.
Follow me on twitter as I explore the world of OSX and my adventures with all things "Hackintosh": @cericsmith
Here's my list:
1Password -- Perhaps the greatest piece of Mac OSX software. You must try to believe it. Password storage/sync/creation/ID management at its finest.
http://agilewebsolutions.com/products/1Password
Unison -- If Windows newsreaders hadn't stopped evolving around 1998, they might have come up with something like Unison in... 2150.
MusicBrainz Picard -- For fixing the "Unknown Artist/Album" issues.
http://musicbrainz.org/doc/PicardDownload
BluePhone Elite -- Neat Smartphone/iPhone tricks with Bluetooth. Ever wanted to have your machine wake up or sleep when you were just out of range? This is an app for you.
Toast Titanium 10 -- Sure, Leopard can burn discs... but Toast is much more than that, and it's elegance exceeds anything on Windows.
http://www.roxio.com/enu/products/toast/titanium/overview.ht...
iLife 09 -- iPhoto's face rec. is just cool, and iMovie beats the snot out of Movie Maker.
Stuffit Deluxe 2009 -- Not as necessary as it used to be, but still nice to have available.
http://my.smithmicro.com/mac/stuffit.html
Parallels 4 -- Many people like VMWare Fusion, but Parallels 4 has support for a lot more configuration of the VM -- support for up to 8 processors, the ability to have VM's start off of CD and/or Disk Image/ISO, is killer.
Little Snitch -- knowing when your applications are "phoning home" is important.
http://www.obdev.at/products/littlesnitch/index.html
DiskWarrior -- HFS+ disk maintanance package and more. Fix disk errors...
http://www.alsoft.com/DiskWarrior/index.html
AppZapper -- Yes, theoretically uninstalling apps on the Mac is straight forward, but AppZaper gets all the flotsom and jetsom that would otherwise be left behind. Great for nuking preference files, etc.
ClamXav -- Ok, we know that Mac's don't get virii, per se... but this cross-platform, donation-ware AV tool gives peace of mind when running random software you download from the Net.
FileSpot -- Spotlight is nice, but FileSpot takes it to another level.
http://mac.synthesisstudios.com/mac/filespot/about
GimmeSomeTune -- integrates with iTunes and pulls/updates album art and lyrics, and works with Growl. Updates iChat status and images based on what you're listening to. Sweet.
http://www.eternalstorms.at/gimmesometune/
HighLight -- Instantly add file(s) or folders to your Spotlight search index.
http://homepage.mac.com/superpixel/highlight/
SimpleComic -- a great comic PDF viewer.
http://dancingtortoise.com/simplecomic/
TED -- This program scours the usual suspects for new TV episodes and integrates with your favorite Torrent program to automatically download them!
DropBox -- 2GB of free, sync'ed cloud storage for your Mac (or PC/Linux box). Incredible in conjunction with 1Password.
http://www.getdropbox.com/install?os=lnx
The Unarchiver -- Ok, so you don't like Stuffit? This will pull apart almost anything.
http://wakaba.c3.cx/s/apps/unarchiver.html
Movist -- A media player based on ffmpeg/VNC that has a more polished UI than VNC.
http://code.google.com/p/movist/ VNC -- open and play anything.
Perian -- Add the ability to open and play most media formats that ffmpeg can handle inside of QuickTime.
Pixelmator -- who needs Photoshop? This $50 application is the bees knees. Cool UI, great features.
doubleTwist -- Part media manager, part file conversion utility. If you need those TV shows on your PSP, this can handle it. Notably, doesn't support iPhone (yet).
http://www.doubletwist.com/dt/Home/Index.dt
MPlayer OSX Extended -- the benefits of Mplayer on OSX. More polished than VNC, more stable (at this point) than Movist.
FreeDMG -- The ability to create Disk Images/.dmg files.
http://www.kelleycomputing.net/freedmg/
Tweetie -- The newest and most controversial OSX Twitter program.
http://www.atebits.com/tweetie-mac/
Boxee -- a "10 foot interface" for managing your media and Internet content sources such as Hulu.
http://www.atebits.com/tweetie-mac/
SuperDuper -- quickly and easily clone your HFS drives.
http://www.shirt-pocket.com/SuperDuper/SuperDuperDescription...
iWork 09 -- Pages is what Powerpoint will never be -- Fun.