Don't you hate it when you're $1 or so short of having a big enough order on Amazon to qualify for free shipping? You feel like you ought to find something cheap to buy to fill out the order, but then you have to wander all over the site looking for something.... Well, now somebody has built a site that will do the searching for you.
Hat tip: Marginal Revolution.
By the way, I'm so happy to see that OCLC is moving towards making the WorldCat data ever more open. I can't wait to see spiffy tools like this being built for library users and not just book-buyers!