I was recently pointed at this collection of new covers for classic books:
http://recoveringtheclassics.com/
There are some nice covers there, but I find the website quite awkward. It is somewhat focused on monetising the covers and seems to lack useful information. You can only download the covers in exchange for an email address, and it's not made clear what you can then do with them (although I guess no-one really cares/knows if I use it for my downloaded Project Gutenberg version in Calibre).
It's a good idea, though, and I wondered if there were any similar collections or projects around?