Book Depository and Gilt
Found about this site via an online class I am taking. Book Depository is an online store that ships worldwide for FREE. There are some advantages and disadvantages in comparing this site to Amazon (e.g. great for purchases under $24.99 though some books are marked at the retail price, unlike Amazon).
In any case, I really like this feature that displays the most recent purchases from all around the world. You can see the dynamic version here.
It is interesting to see the different book titles spanning from gastroenterology to games to romance, which are plotted across different continents. I saw at one point a couple of purchases of the same title in the UK and in Australia, and not sure if this tool was working, or if they were in an online book club or online class. As simple as the interface is, I think this is a great tool for discovery.
Another site employing a similar technique is gilt (see live version here).