Kaspersky Online Scanner:
If you discover a suspicious file on your PC, or suspect that a program you downloaded from the Internet might contain malicious code, you can check the files using the free Kaspersky File Scanner. Using Kaspersky Anti-Virus technology, any file you send to Kaspersky Lab will be checked for viruses, Trojans, spyware or other malicious code.

Trend Micro HouseCall:
Scan Now. It’s Free
Trend Micro HouseCall is an application for checking whether your computer has been infected by viruses, spyware, or other malware. HouseCall performs additional security checks to identify and fix vulnerabilities to prevent reinfection.

BitDefender Online Scanner:
BitDefender Online Scanner is an on-demand virus scanner which incorporates the award-winning BitDefender scanning engines. You can use it to scan your system’s memory, all files and drives’ boot sectors, and to automatically clean infected files.

ESET Online Scanner:
The ESET Online Scanner is the Web’s best free virus scan. A user-friendly, powerful tool, our online antivirus utility can remove malware—viruses, spyware, adware, worms, trojans, and more—from any PC utilizing only a web browser. No installation required. The scanner uses the same ThreatSense technology and signatures as ESET NOD32 Antivirus, which means it is always up-to-date.

Panda ActiveScan:
ActiveScan is an advanced online scanner based on Collective Intelligence (scanning in-the-cloud) that detects malware that traditional security solutions cannot detect.

McAfee FreeScan:
McAfee FreeScan helps you detect thousands of viruses on your computer. Based on the award-winning McAfee VirusScan engine, FreeScan searches for viruses, including the latest known “in the wild” viruses, and displays a detailed list of any infected files. Should viruses be found, FreeScan even provides links to more information about the viruses and what you can do to clean your system.

F-Secure Online Scanner:
F-Secure Online Virus Scanner is a free service. Use it to find out if your computer is infected, and disinfect your computer if needed. The product will automatically download the necessary components and virus definition databases as it is started.