I us CA(Brand.... Not sure what the specific one is) and eTrust Antivirus and Norton(JK).
I also have zone alarm internet protection
Umm they all costs money though but works really well.
My friends will swear my MacAffee though which is free, so I recommend that one for you.
As far as other programs go, I use Adobe Products (I design webpages for money) so try photoshop (I know its expensive), I have a couple games (i.e. Starcraft and Tremulous), but I don't have anything to speed up my computer (i don't trust half of them and my comp is beast enough to handle almost anything I throw at it [except Crysis on High

])