I use Avast! and AVG Free for AV.
Using Online Armor for a firewall. It's still a bit buggy but the dev team at tallemu are sorting things out rather quickly. I have the latest beta which works really well so the next release will definitely be worth it. It only supports XP currently but they are working on a Vista release.
Comodo + Avast!, although Avast! still has a lot of false positives, but less than others. Stay away from Norton - chows resources like crazy and even sees itself as a virus.