CheckYourNetwork.net - Free Online Virus Checking and Testing Tools

Trendmicro.com - The Leaders in VIRUS Checking
    Give your PC a FREE check-up! HouseCall is a demonstration of the power of Web-based technologies that Trend Micro is developing to make deployment and management of virus protection in corporate settings fast and easy.

Be Sure to Check out Clustered Networks Untangle Security Appliances

The Untangle Gateway, the world's first commercial-grade open source solution for blocking spam, spyware, viruses, adware and unwanted content on the network, provides a free and better alternative to costly, inflexible proprietary appliances. Untangle's applications are currently being used in tens of thousands of businesses in a variety of industries, including financial services, real estate, education, bio-science, and professional services.