Sophos are offering a free product for mac users at home. You can grab it from here
Their blurb says
Full Mac protection from viruses, Trojans and worms
- Easy installation and painless maintenance
- Business-quality antivirus, backed by SophosLabs
- 100% free! Totally, absolutely, completely
- Supports OS X 10.6 Snow Leopard and up
So why not treat your mac to a little antivirus TLC ?