MacOS X Software

uControl - http://gnufoo.org/ucontrol/ - GPL
allows you to remap capslock to control. also gives you the ability to do Fn+trackpad as a virtual scroll wheel function.

Monolingual - http://monolingual.sourceforge.net/
free 600MB+ by deleting support for languages and input methods that you know you will never use.

StarfishX - http://homepage.mac.com/mscott/starfishx/starfishx.html - GPL
generates interesting background patterns.

ShadowKiller - http://www.unsanity.com/haxies/shadowkiller/ - freeware
removes the shadows around windows, can speed up the interface.

Text Extras - http://www.lorax.com/FreeStuff/TextExtras.html - but it supposes to give all Cocoa-based apps emacs-like keybindings in input dialogs, and access to several internal features.

opensource screen savers - http://s.sudre.free.fr/Software/WBSoftware.html - open source
a bunch of screensavers. the SaveHollywood screen saver is interesting because it can display a flash animation or quicktime movie. which can be useful for product demonstrations or a mac-based kiosk.

Onyx - http://www.titanium.free.fr/english.html - freeware
lets you control many internal features (mostly gui features) of OSX.

Growl - http://growl.info/
gives applications that support it a configurable way to provide alerts (instead of having bouncing icons in the dock)

FullScreen Player - http://home.netvigator.com/~feelorium/feelorium/FullScreenPlayer/
lets you watch quicktime movies full screen without buying the full version of quicktime ($12 shareware). you could probably spend a couple hours looking at the source to SaveHollywood screen saver and write your own thing that does the same.

TemperatureMonitor - http://www.bresink.com/osx/TemperatureMonitor.html - (shareware?)
watch the temp of your Mac. g3/g4 can only watch the harddrive temp. g5 has an on-die cpu temp and case temp as well.

Fink - http://fink.sourceforge.net/ debian-like package installer for various opensource apps.

Darwin ports - http://darwinports.opendarwin.org/
freebsd-like package installer for various opensource apps.

MPlayerOSX - http://mplayerosx.sourceforge.net/ the #1 video player on Linux comes to OSX. With the interesting ability to play movies in place of the desktop wallpaper. Note that burried within the .app directory there is a normal mplayer binary that you can symlink to and use in the traditional Unix way.

divx codec for quicktime - http://www.divx.com/divx/mac/

xvid codec for quicktime - http://people.ee.ethz.ch/~naegelic/download/ - open source
a video codec for mpeg4

ffmpegx - http://homepage.mac.com/major4/
convert between video/audio formats

Mac OS X speed FAQ - http://www.macmaps.com/Macosxspeed.html

SharePoints - http://www.hornware.com/sharepoints/
allows much more customized control over the samba configuration in OSX. share directories other than Public/ folders

AquaLess - http://aqualess.sourceforge.net/
less/more pager in a gui

XNMap - http://homepage.mac.com/natritmeyer/
nmap in cocoa. a bit more powerful than the "Port Scan" tab in NetworkUtility

zipdrop - http://osxutils.berlios.de/
the best way to create ZIP files in OSX (opensource)

OSXvnc - http://www.redstonesoftware.com/vnc.html
vnc server for OSX. this company sells an interesting gui testing product that uses vnc to test Mac, Windows, Linux, etc.

Freecell - http://wasters.org/freecell/ - open source
finally the last reason to use MS Windows has been removed.

MacOS X Hints - http://www.macosxhints.com
A hodgepodge collection of articles covering almost every issue you have ever had with your Macintosh.

wClock - http://www.wolfware.com/wClock.html - freeware
A nice simple menubar clock application that is substantially less braindead than Apple's.