The coolest thing about DiscTop is that when you insert a known DVD (say, The Simpsons Movie) you can set the artwork via an Amazon search and display it over top of the DVD icon. DiscTop even asks you what type of Mac you use and then positions the disc accordingly. For instance, I have an iMac Core Duo (early 2006 model), so when I use that profile DiscTop will make sure the disc's icon is positioned where the optical drive is located. Very cool!
If you want to give DiscTop a spin it's freeware and available at the developers website.