Open Source Software (OSS) for Macs is an oft-neglected topic so hopefully the recommendations below will serve to go some way to redress that imbalance!

well-known oss applications also available for osx

• **Audacity** (sound recorder & editor)
• **Firefox** (web browser)
• **FreeMind** (mind-mapping program)
• **The GIMP** (image editor)
• **Handbrake** (DVD ripper and video converter - formerly OSX-specific!)
• **KompoZer** (web page editor)
• **Miro** (HD video player & Bittorrent client)
• **OpenOffice.org** (and **NeoOffice** - office suites)
• **VLC** (versatile video player)
• **XMind** (mind-mapping program - can host mindmaps online)

oss applications that are osx-specific

• **Adium** (instant messaging client)
• **Cyberduck** (FTP client)
• **ffmpegX** (video transcoder)
• **Q** (an emulator allowing Linux, Windows and other operating systems to be run in a virtual machine)
• **Quicksilver** ('unified, extensible interface for working with applications, contacts, music, and other data')
• **Romeo** (control Mac via Bluetooth)
• **Seashore** (image editor)
• **SimplyBurns** (CD/DVD burning software)
• **Transmission** (Bittorrent client)

MacLibre

A wonderful, wonderful suite of programs is available for OSX called **MacLibre**. This features a wealth of OSS, auto-updates, and is a graduate of the Google Summer of Code competition. I would recommend any Mac user to install this - what have you got to lose?
More Open Source software for OSX is listed at **Open Source Mac**. A more comprehensive list is available, of course, at **Sourceforge**.