Anti-Virus / Anti-malware for Macs

Nowadays even Macs can get viruses, or get infected by trojan software, sowe'd recommend you download of of these and run it regularly:

Free:
Avast: http://www.avast.com/free-antivirus-mac
Sophos Anti-Virus for Mac: http://www.sophos.com/en-us/products/free-tools/sophos-antivirus-for-mac-home-edition.aspx

($$)
Norton AntiVirus for Mac http://buy-static.norton.com/norton