Being in the military allows me free use of Symantec corporate edition, with unlimited support. Its pretty nice and something I wished they would advertise more to persons in the military. Speaking of which,
Any of you Army personnel reading this. Do a search for Computer Emergency Response Team or ACERT and log on to the website using your AKO logon. Then go to the tools section and download your AV software from either Symantec, or McAfee and I think one other. You can also DL Symantec's software fireewall. I personally really like the firewall, easy to use and fairly thurough.
I also use Lavasoft Ad-Aware SE, Spybot SD, and on occasion HiJackThis.