Here's a list of all the coolest open source software I could find. For all those people who don't want to or just can't afford to pay for Software! But if you can afford to donate a bit of change to help them out I would strongly encourage it.
AbiWordWord processing software simmilar to NeoOffice but without all the other programs.
AcqliteGnutella file shareing app with no spyware or ads.
AdiumThis is one of the best IM programs out there. Allowes you to connect to multiple servers including AOL, MSN, Yahoo, ICQ and more.
Armagetron AdvancedA 3D Game modeled off the Movie tron.
AudacityA simple sound recording and editing program.
Blender3D modeling Software.
CaminoWeb browser similar to Firefox but designed only for the Mac. It's agreat browser but Firefox is still my Favorite.
CashboxPersonal Finance managing program with some of the same features as Quicken.
CenterStageTurn your Mac into a Media Center that you can connect to your TV. You'll need at least a G4/G5 processor. and OS X 10.4. I think this would be a great program if you had a Mac Mini but I haven't had the chance to try it on one yet.
Celestia3D Planetarium software that recreates the experience of traveling through space.
ColloquyThis is a really cool IRC client.
CubeFirst person shooter game.
CyberDuck
FTP and SFTP file browser for the Mac.
Democracy Internet TV PlayerBuilt in Channel Guide with over 300 channels. Whatch video from Podcasts, RSS Feeds, Blogs, Web sites and more! All in full screen.
FirefoxHonestly the best web browser I've found for the Mac (or even that other opperating system). Includes Tab browsing, plugins and support for almost all websites (including secure bank sites).
FreeMindReally cool note taking/mind mapping program.
Gimp.AppAn easy to install and use Image and Photo editing program simmilar to Photoshop. I love this program!
HandBrakeDVD Ripping software that also converts into MPEG-4 and other video formats.
iPod DiskiPod Riipping software that lets you get music off your iPod just like a regular disk drive.
Inkscape
Vector Graphics editing program simmilar to Illustrator and CorelDraw.
JomicThis program alowes you to read online comic books from comic book archives.
JuiceListen to your Podcasts when you want.
MPlayerPlay all the media file types you want in one media player.
NeoOfficeThis office suite has everything you need including word proccesing and spreadsheets. IT's compatible with Word and OpenDocument file formats.
NVUWeb Site creating program simmilar to Dreamweaver.
Open SongThis is a great alternative to using Keynotes or Powerpoint to display songs in your Church, School etc... It allowes you to select different backgrounds and display Bible verses. I use this program all the time and I highly recomend it.
RSSOwlThis is a great cross platform RSS/Atom reader. If you use multiple Operating Systems but want to use the same RSS reader then this is the one for you!
SenutiiPod Ripping software.
SmultronText/HTML editor.
StepmaniaDance Dance revolution clone. You can play this game using a keyboard but you will need a dance pad to really enjoy it.
ThunderbirdThis Email app is from the creators of Firefox and will meet any expectations you have as a result. It has great Spam Filtering and you can even customize the look and feel to suite your needs.
TransmissionBitTorrent program with an easy user interface.
ViennaGreat RSS/Atom feed reader.
VLCMedia player that will play more file formats than Quicktime.