Coverflow is a shiny piece of eye candy for Mac OS X iTunes listeners. It gives you a nice simple and attractive way to flip through your album covers one at a time and then play what you see. See a review on Cool Hunting.
If anyone wants to do a mashup, here's a library idea - take a good easy to parse catalog interface like John Blyberg's AADL REST interface and hook it up to something like this so that you can flip through book covers just the same way. Or even do cover art for new books with a flip-interface through the RSS interface from Steal This Library, or your own personal collection from LibraryThing.