AVG is the best FREE antivirus software. It isn't the best, though. If you're willing to spend a little money for a subscription (like you must do with McAfee), I would explore these sites:

http://www.eset.com/index.php
http://www.f-secure.com
http://usa.kaspersky.com/products/anti-virus.php

Good Luck

Dano

P.S. I'm sure you have already done so, but please make sure and read all of the stickies in the forums...they can greatly reduce (or eliminate) the likelihood of you downloading malware.