Addressix is the perfect program for printing envelopes. It uses the Addressbook. (kinda didn't have a printer for a while so I stopped using it)
Spy puts a well designed CPU monitor in the menubar. (no longer using) iPulse does the same thing but with the Dock and is Way Way Complex, visually. I prefer Spy's increasing revolutions for increasing load, but iPulse has its own neat style.
ASM by Frank Vercruesse put the MultiFinder menu back where it belongs. (no longer using)
TinkerTool lets me place my scroll arrows "Together at both ends" as well as make hidden applications transparent in the Dock.
WindowShade X is, well, WindowShade for OS X. Double-click the tititle bar to roll the window up like blinds instead of minimizing to the Dock.
Final Vinyl records with an iMic.
I used ID3X when I needed to set the track number tag using data in the filename. Yay batch!
Bwah! This program is great! OmniOutliner rules! Download and buy it, soon.
Nisus Writer Express is the modern revision of this classic Macintosh word processor.
PuzzlePalace is a graphical frontend to OpenSSL for one at a time drag and drop file encryption.
DVDBackup lets you watch movies without spinning the disc drive.
Related, Handbrake takes the extra step of creating an mpeg from the DVD data, whether stored on disc or on disk.
Thumbnail Pro is great at creating the type of thumbnails I want.
Wakeup from Coriolis sends a wake-on-lan packet out to wake up the specified MAC address. Just like etherwake.
Salling Clicker Too Bad Ass. Turn your Bluetooth phone into a remote control for iTunes, iPhoto, PowerPoint, DVD Player... pauses music during calls, pops up caller-id onscreeen so I know who's calling before the phone is out of my pocket...
A better interface than the QuickTime Pro I paid for and with additional codec support, VLC is the best Mac OS X media player I've found.
Of course all the Microsft tools are at Mactopia; the only useful one is Remote Desktop but Windows Media Player is a requirement.