xfreeware.com: Mac OS X Freeware

Butler

http://www.petermaurer.de/

This is probably the most awesome app ever conceived. Contains most of the functionality of LaunchBar and Quicksilver + several other apps too, all with a tiny memory footprint.

MenuMeters

http://www.ragingmenace.com/

If you like to keep an eye on CPU use, bandwidth, mem usage, this will give you the readouts. Essential on every working person's Mac.

Camino

http://www.caminobrowser.org/

Fast, slick browser, and very functional too. Based on the open source Gecko core, but has the OS X appeal.

VLC

http://www.videolan.org/vlc/

The swiss army knife of video players. Can play almost everything except new WMVs. I use this instead of Quicktime Player 99% of the time. Required.

Almost all of the features of Photoshop at an infinitely smaller price. Based on the GIMP base, but with a more Photoshop-like interface. Requires X11 but you can find that on your OS X install disc. And they just released a Universal Binary too.