Secunia is one of the many security firms who maintain teams of researchers looking for vulnerabilities in software applications. I have seen their name credited on several vulnerability notices from CERT and SANS. They offer a software vulnerability tool called Secunia Personal Software Inspector that is free for personal use. It scans your system looking for all executable files and then compares them to their database of current software versions/vulnerabilities. I have used it on a couple of systems that I believed to be current and found at least half a dozen out-of-date or vulnerable apps. Apart from the security benefits, it can also be an easy way to see if there have new releases for any of your software. For example, Secunia PSI informed me that a new version of Wireshark was available for my home computer even though it didn't find any security vulnerabilities for the version I was using. This can be much easier than individually opening each app and clicking on "check for updates", or even worse, having to go to the app's website to see if a new version is available.