Secunia PSI 3.0. It monitors your entire computer for software updates, and notifies you if you have any software that is outdated and that there are software updates available. It actually updates most of the software itself, but for those that it cannot, it will notify you that you need to do so.
The Secunia PSI explained
The Secunia Personal Software Inspector (PSI) is a free computer security solution that identifies vulnerabilities in non-Microsoft (third-party) programs which can leave your PC open to attacks.
Simply put, it scans software on your system and identifies programs in need of security updates to safeguard your PC against cybercriminals. It then supplies your computer with the necessary software security updates to keep it safe. The Secunia PSI even automates the updates for your insecure programs, making it a lot easier for you to maintain a secure PC.
Using a scanner like Secunia PSI 3.0 is complementary to antivirus software, and as a free computer security program, is essential for every home computer.