From a message that I received, apparently some wish the web sites for the FREE anti-virus programs. (And I've thrown in a couple of good anti-spyware, anti-adware programs.)
If you go to any of these sites, be sure to use, or navigate to, the FREE version. They are adequate for most users. The primary difference (in most) is that you need to update every week or so. With the current worm threat, I'd update frequently, just to be sure. All these companies have paid-subscription versions, but the main difference is they will update automatically and their C.S. may be more available.
AVG Anti-virus: http://free.avg.com/download?prd=afe
(You want the FREE AVG, not
the "Premium Protection Free", which does not turn out to be actually free.)
Avast! Anti-virus: http://www.avast.com/eng/avast_4_home.html
Most everyone already knows this, but do not install more than one Anti-virus program on your machine---they will conflict with each other. That rule does not apply to anti-adware/spyware programs.
These are anti-adware/spyware programs. They have no anti-virus function:
Lavasoft Ad-Aware: http://www.lavasoft.com/home.php
Spybot Search & Destroy: http://www.safer-networking.org/en/mirrors/index.html
Hope this makes finding the a/v program sites a little easier!