Avira AntiVir Personal Edition is free, but limited.
http://www.free-antivirus.info/anti-virus/antivir-personal-edition.html
AOL Active Virus Shield (Kaspersky Antivirus). AOL does not specify whether the product is time-limited. However, the initial expiration date in the program license info is set at one year from the date of installation.
http://www.free-antivirus.info/antivirus/aol-active-virus-shield-kaspersky-antivirus.html
Just a couple more. Although I prefer my AVG Free.