The Open Media Collectors Database (OpenDb) is a PHP and MySQL based inventory application that allows you to easily catalog and lend out your stuff. Its primary purpose is to catalog media related items, such as DVD's, Books, CD's etc, but its so flexible you can use it to catalog pretty much anything.
Opendb ships with many media related (DVD, VCD, CD, VHS, games, books, and laser discs.) item type definitions, or you can download a user contributed item type or create your own.
The following is a non-exhaustive list of the functionality included in OpenDb 1.5.