Abandoned Village Mine

Abandoned Village Mines can only be found in large villages that are located right by a cliff or a mountain. It is almost like a Mineshaft, with rails and minecarts, but no cave spiders.

What makes this really good is that it has plenty of emeralds, even in y levels that you don't find them in.

There is also always a minecart with a chest in front of the mine, with pretty decent loot. Here are all the items that could possibly be in the minecart:
 * Emeralds
 * Enchanted Books
 * Coal
 * Charcoal
 * Cobwebs
 * Flint