The free edition of AVG Anti-virus is one of the most downloaded free anti-virus software. They have released the latest version 10 (2011). This includes
Anti-Virus , Anti-Spyware, Smart Anti-Rootkit (ENHANCED) - Makes sure you can’t receive or unintentionally spread even the toughest viruses or spyware
AVG Social Networking Protection - Protects you and your friends on social networks
AVG LinkScanner (ENHANCED) - Checks web pages in real time before you visit them and shows safety ratings in your search engine results list
Read more about the product here
Download AVG Anti-Virus free edition 2011
Download AVG Anti-Virus free edition 2011 - Offline installer