LibraryThing has this funky “view all your covers” feature.
So I fired that up and then did a little screengrab of the complete page. The books that don’t have covers (out of print or foreign books) don’t get included, but still – you can see the covers of something close to 900 books in one image. It’s pretty sweet.
(You’ll have to click to enlarge to full screen size, btw.)