"HandBrake is an open-source, GPL-licensed, multiplatform, multithreaded DVD to MPEG-4 converter, available for MacOS X, Linux and Windows."

Some very useful utilities. Service Scrubber helps you manage OS X services, Witch turns command+tab into something that can access the windows of individual applications, not just the applications themselves.

Play Divx, AVI, and tons of other video formats in QuickTime.

"A Mac OS X bridge application between Adium IM and Address Book used to search, manage and keep your contacts in sync. "