World Trade Organization (WTO)

The World Trade Organization (WTO) is an intergovernmental organization based in Geneva, Switzerland that "deals with the rules of trade between nations at a global or near-global level."  Born in 1995 under the Marrakesh Agreement, the WTO continues the liberalization process started by the now defunct General Agreement on Tariffs and Trade (GATT from 1947) and is currently comprised of 153 countries.

Map (from Wikipedia, dark green = original member, light green = subsequent member) :

Please see this link for information on the WTO's structure and successes.
Please see this link for the pros and cons of the WTO.  They're pretty straight-forward and logical.