X Freeware

Google Earth

http://earth.google.com/

If you don't know what this is yet, you've been under a rock in the middle of Australia. Check out your house with this.

HandBrake

http://handbrake.m0k.org/

This is the VLC of DVD video encoding. It will take a DVD and convert it into almost anything else. Handy for if you want to take your laptop on the road, but dont want to carry all your DVD's too.

MidiKeys

http://www.manyetas.com/creed/midikeys.html

Lets you use your computer keyboard to send MIDI signals. Awesome to turn your Mac into an instant synthesiser or drum machine instrument! Check out Rax too.