Secunia Personal Software Inspector (PSI) is now officially out of beta and at version 1.0 (well, OK ... version 1.0.0.1). I have used versions prior to 1.0 and found them excellent. I'll be downloading, installing, and running PSI 1.0 today. I encourage you to do the same. This free software checks your programs for any updates.
While Microsoft Update (or the lesser Windows Update) does a great job, they naturally only deal with Microsoft products. Your computer has tons more programs, each of which may need a security patch, bug fix, or enhancement. Why check them all manually? Let PSI check for you. Try it; you'll like it.
To really stay on top of patches, I also use Driver Detective (not free, but very worth having).