avast! 4 Home Edition is a full featured free anti-virus software strictly for home and non-commercial use.

avast! 4 Home Edition has many more features than most other free anti-virus tools such as scanning emails and news servers for virus threats at the protocol level, ie. SMTP/POP3/IMAP4/NNTP. avas! 4 is also capable of protecting against viruses from instant messaging and P2P sources.

There is also a version available for Linux.