ive got some more cool open source programs which i use:
Tuxguitar - free alternative to Guitar Pro, it even opens up all guitar pro files.
Songbird - iTunes like media player with cool add ons
Ardour - Professional audio workstation (Mac + Linux only)
GIMP - If Photoshop were free it would be called GIMP
VirtualBox - Like VMware but free.
Bluefish - Similar to Dreamweaver.