I use AVG Free Edition at home and on our non-business laptop.
For my laptop, office PCs, and servers (since I'm 100% legal), Trend Micro Worry-Free Business Security Advanced. This software is amazing. Not only does it hook up seamlessly with Exchange and each PC, but all security updates are performed automatically from the server so that the network isn't affected. Love it, love it, love it. And it's only about $40 per license per year.
VIPRE by Sunbelt out of Tampa. Have had the other well known. But after installing VIPRE it found stuff the others didn't. Also freed up 10% more space and no troubel with Service Pack-3. As for firewall, ZoneAlarm. AVG freeware on the desk top downstairs. IMO, VIPRE is excellent! Not that expensive either.