Spinebreakers is a site sponsored by Penguin Books which appears to be bringing print publishing up to Web 2.0 sensibilities. It's interesting because traditional print publishers need to keep up if they don't want to become irrelevant, and Penguin Books seems to be doing the right stuff. Between initiatives like Paper Cuts, a competition to get kids to write 100 word essays on what really matters to them and collecting the best ones into a printed volume, to fantastic cover design for classic reprints, they're doing the right stuff.
(And speaking of visual design for book jackets, be sure to check out the Penguin blog, which celebrates print design with articles like this one about designing the covers for a series of horror novel reprints. Good stuff.)