The Serious Eats Guide to Sandwiches
Here is an excellent tour of all sorts of sandwiches, from the classics like BLT and Club to Greek Doner Kebab and Dutch Crunch. The descriptions are based on the sandwiches as cooked in different parts of the US, but, I think, that would be pretty accurate for other parts of the world as well.
Warning: some seriously yummy pictures ahead!
Via kottke.org.