Major League Gaming's upcoming Dallas event will play host to the first ever Halo 3: ODST public play session. There'll also be Major League Gamers doing their thing, but why watch when you can play?
The ODST station's open on August 29, and you'll have to register for a time slot if you want in on the action. Entrance to the show costs $20, though, so unless your life somehow hinges on your ability to play ODST early, you might want to consider dropping said coin on a copy of the game instead. It's out in September, in case you haven't been blitzed by a marketing campaign yet.
So that's that.