Lucien is a Book/Movie/Comic Inventory system written in PHP. You can use it to Inventory non-media stuff, if you want as well. One of the best features is that it lets you use a barcode as input. This means you can use your smart-phone to add a barcode to the search URL, and use that to help inventory easier.
This is the working 1.0 version. I have a 2.0 coming out, but that's a ways away.
There be dragons in here, especially in the search and results.