I've been using this awesome application to keep my Books, DVD, VHS, CD and complete video games organized. It's called Delicious Library and it uses a nifty barcode scanner to read read the UPC code right of your boxes.
http://i4.photobucket.com/albums/y13...ne/Screen3.jpg
Once scanned in, you'll hear the computerized female voice repeat the title and it displays your collection on a 'virtual shelf' and gives you tons of information it downloaded using the barcode information; including a high-res image, retail price and current value!
http://i4.photobucket.com/albums/y13...ne/Screen5.jpg
http://i4.photobucket.com/albums/y13...ne/Screen1.jpg
http://i4.photobucket.com/albums/y13...ne/Screen2.jpg
It gets the information from the Amazon.com database and obtains the current value by looking for the lowest priced copy currently being sold, and given Amazon's typically high prices, I'd call that as close to accurate as can be expected by an application such as this. You can also reload the information on any title at any time. Also, it lets you upload your library and all associated info from each title to your iPod's 'Notes' folder.
Depending how often you loan your stuff out, it also acts like an actual library, and allows the user to "check out" items to borrowers and even assigns due dates.
Unfortunately, it's only available for Macintosh, but I have to say, it's one of the coolest ways to catalog your stuff.