Back in the old days of CNET, we had a product I loved called CNET Catchup. It scanned your computer and told you which software on it had updates available. I'm happy to report that we've brought the function back, in a completely new product called TechTracker.
It's a free app. It will scan your PC (at regular intervals if you like) and tell you what you have that's old or out of date. It gives you links to updates as well as user reviews of the apps. Updates come to you from our Download.com site, so you know they're safe and spyware-free.
The Windows version is in public beta (get it here). A Mac version should be out soon.
This is not an impartial expert review. We don't review our own apps. This is a pure pitch. I like TechTracker and I'm proud of the team here that built it. So go get it and tell the folks who made it what you think.