Well, I can think of two other opensource programs I like:
Clam AV
(open source virus detection program)
http://www.clamwin.com/content/view/18/46/
And you get automated virus updates too. No nag screens asking you to pay your protection money either. I know viruses suck, but damn - the antivirus subscriptions almost feel like you are paying the mob protection money...
And GIMP
A Photoshop like program
Heh - the 'comics' I do have so far all been done in GIMP
http://www.gimp.org/windows/
Very powerful