Circle Six Design names LicenseKeeper as one of their top 10 Mac Utilities in 2007.
LicenseKeeper simply lets you add an application and record some metadata for it, including purchase price, links, and a license or serial number. It can attach files and emails. In fact, my favorite feature is the email scanner, which will grab the selected message in Mail, attach it to the entry and scan it for serial numbers. If it finds one it will update the serial number field with the information.