Loving this. It's the delicious Book Cover Archive - "an archive of book cover designs and designers, for the purpose of appreciation and categorization". It's got a heavy US slant at the moment, but that may change as they put more stuff up. You can check out their rather good blog too.
If you're looking for some other book cover goodness, check out The Book Design Review, and Covers from Fwis (who have a searingly honest way of structuring their site).
