Claimdog is a new online service that tracks down money owed to you. I tried it this morning and found out that my wife was owed some kind of settlement check for $103.60 from an insurance company from over 20 years ago. They charged me $10 for the service, which seems reasonable for how easy it was to claim the money. (Missing Money is a free site, which you can use if you are willing to file a claim yourself.)
Try it yourself, and if you strike it rich, let us know in the comments!