Straight from the WoW homepage:

We have some exciting news to share with the world's most skilled Arena System combatants. This year's regional World of Warcraft Arena Tournaments will feature two sets of qualification rounds played out on special tournament realms in each region. These rounds will culminate in live regional and world finals events, with a mooncloth bag's worth of cash up for grabs... to the tune of a total prize pool of more than $200,000.

And no news post would be complete without linkies!  Here's the FAQ, and the full announcement!  Good luck to all who enter!  May the best in Azeroth win!