The long-awaited Duke Nukem will be released in the US on 3 May 2011. The rest of the world will be able to grab a copy from developers Publisher 2K Games and pinch-developer Gearbox Software on the 9th May.
2K Games says to expect a demo at some point. If you want it early, you'll have to join the Duke Nukem Forever First Access Club, which means spending extra cash up front: The access codes are only available in Gearbox's Borderlands: Game of the Year Edition.