It’s rare that such an online tool gets me this excited and if you fly (like, ever) this is a great tool for you. FareCompare lets you set any international home city, and they lists the cheapest prices to any city in the world you can imagine. It even gives you a 12 month history of the ticket prices. FareCompare goes through all of the major online ticket retailers for you.
Personally, I thought the Google maps it creates with a price next to each city was very cool indeed – and this Firefox extension.
Before you fly, check it.