Free Downloadable AntiVirus Utilities

Kaspersky Virus Removal Tools
Kaspersky has made a number of virus removal tools available for free download. These tools address specific computer virus, worm and trojan threats

Comodo AntiVirus
Comodo AntiVirus 1.1 beta provides heuristic analysis, real-time on-access scanning and automated daily updates. According to the website, all future releases will also be free antivirus software.

BitDefender Free Edition
BitDefender Free Edition is a basic on-demand virus scanner.

Malicious Software Removal Tool
The Microsoft Malicious Software Removal Tool is an anti-malware utility that checks computers running Windows 8, Windows 7, Windows Vista, Windows XP, Windows 2000, Windows Server 2012, Windows Server 2008, and Windows Server 2003 for infections by specific, prevalent malicious software—including Blaster, Sasser, and Mydoom—and helps remove malware and any other infections found.

ClamWin Free Antivirus
ClamWin is a Free Antivirus program for Microsoft Windows 8/ 7 / Vista / XP / Me / 2000 / 98 and Windows Server 2012, 2008 and 2003. It does not include an on-access real-time scanner

Clam AntiVirus
Clam AntiVirus is a GPL anti-virus toolkit for UNIX. The main purpose of this software is the integration with mail servers (attachment scanning). The package provides a flexible and scalable multi-threaded daemon, a command line scanner, and a tool for automatic updating via Internet. The programs are based on a shared library distributed with the Clam AntiVirus package, which you can use with your own software. Most importantly, the virus database is kept up to date .

Avira Free Antivirus
Avira Free Antivirus is available for Windows, Mac and Android. It is the free version of a commercial product (for example, the Windows version doesn't scan email attachments). Check the website to see which features are available in the free version.

Ad-Aware Free Antivirus+
Formerly just an adware and spyware remover, this now includes anti-virus in the free editions, which naturally has some limitations.

AVG Free Edition
AVG Free Edition is still around, but the feature set is pretty limited.

McAfee AVERT Stinger
Stinger is a stand-alone utility used to detect and remove specific viruses and worms, including Lovsan. It is not a substitute for full anti-virus protection, but rather a tool to assist administrators and users when dealing with an infected system.

avast! 4 Home Download
avast! Home is now free of charge for HOME users for NON-COMMERCIAL use. (Windows)

F-Prot Antivirus
Free versions for home users of Linux, FreeBSD, Solaris. There is also a command line DOS scanner, but the Windows version is not free.