I discovered this great new programme t'other day.. its called "Books", and is a very cute little freeware database for books (does exactly what it says.. blah). Its really cool cos it downloads the details very much like Gracenote does for itunes.. and there's a section where you can write who you have loaned books to. I'm sure it would work for DVD too. Not sure it works on Windows but!
oooh yes, find it via www.FreeMacWare.com