Antivirus online y gratis.

Antivirus online:

ESET (Nod32) Online Scanner
Panda ActiveScan Online
BitDefender QuickScan (escanea virus pero no los elimina)
Kaspersky Antivirus Online

Antivirus gratis (Free Edition): Requieren instalación.

Panda Cloud Antivirus Microsoft Security Essentials
Microsoft Security Essentials
Avira AntiVir Personal Edition
AVG Anti-Virus System Free Edition
BitDefender 10 Free Edition
Norton Security Scan

AntiSpywares gratis (Free Edition): Requieren instalación.

Dr.Web CureIt!