This is a comprehensive list for free antivirus :
Avira Antivir Personal – Free Edition

Download Avira Antivir here
PC Pro wrote :

A free package that scores highly, beating almost all its big-name competition. It certainly attracted our attention this month, when its free PersonalEdition Classic product achieved a remarkable 92% detection rate in our tests. We rarely saw AntiVir make much of an impact on our CPU usage, but even when told to scan only executable files it still caught non-executable malware once we double-clicked on it. AntiVir is the most effective free antivirus package we’ve seen.

You can update it using automatic update or you can download AntiVir incremental VDF update here

avast! antivirus Home Edition

avast! antivirus Home Edition is FREE to use but it is necessary to register before the end of the initial 60 day trial period. Following the registration you will receive by e-mail a license key valid for a period of 1 year. After you have downloaded and installed the program, the license key must be inserted into it within 60 days

avast! Home Edition was voted “Best Bet” among free security tools by PCWorld magazine. The editors were especially impressed that avast! includes 7 different resident shields which protect a user’s PC, with minimal impact on system performance.

AVG Anti-Virus Free Edition

AVG Anti-Virus Free Edition 8.0 has won its first award, PC Pro recommended. A great update to an already-popular package. If you want a free antivirus product, AVG Antivirus Free Edition 8.0 is the one to download.

BitDefender Free Edition

Download BitDefender Free Edition here

Suggest me if you find interesting free AV.