ESET Online virus scanner:
http://www.eset.com/online-scanner
No need to download anything, it will run the virus scanner within your browser. It is made by the develepers of the popular anti-virus software 'NOD32' and it should pick up most virus' out there.
Malwarebytes Anti-malware
http://www.malwarebytes.org/
Free software you need to download. You can then run a thorough scan of your system and it will pick up any virus' remaining on your system.
AVG Antivirus
http://free.avg.com/gb-en/homepage
AVG is one of the most popular free anti-virus programs around. Its updated frequently, and will pick up most virus'
Avast! Antivirus
http://www.avast.com/free-antivirus-down…
Probably the second most popular free anti-virus software after AVG.
Spybot search and destroy
http://www.safer-networking.org/en/index…
Its not an anti-virus as such, but its a very useful software to have because it includes alot of various tools for searching and finding spyware, malware etc.