In my day to day operations and learning process I came across the following useful link from the team at Mozilla i.e. the Firefox people:
This link checks on all of the browser plugins installed on you machine and informs you whether or not they are up to date.
It works for Firefox 3.6, Opera 10.5,Safari 4, Chrome 4 or I.E 8
Since a large number of the security vulnerabilities that are reported are related to issues with various plug ins, particularly Adobe Flash, I believe this a very valuable resource for the I.T pro community to be aware of.