Secunia Software Inspector

Any software can have security vulnerabilities that allow remote attackers to compromise your system. While Microsoft updates (when they work) offer a one-stop shop for Windows patches, there are dozens of other vulnerable products that need to be patched regularly as well. Secunia Software Inspector is a free online service that scans the system for vulnerabilities in some of the most widely used software, providing a detailed list of what needs patching and even where to get the necessary patches.