Tower Defense-style games are beginning to crop up more and more - all desperate to hit that same sweet spot between lunchtime casual and mouth-foaming addiction typified by Desktop Tower Defense. At PAX , Microsoft Game Studios & Hidden Path will be deploying Defense Grid: The Awakening - a glossy take on the genre for XBLA featuring all the key ingredients: lots of enemies & loads of different turrets and weapon emplacements to blow them up with, all strategic-like. The game has an impressive-sounding pedigree. Designed by Mark terrano (previously responsible for Age Of Empires II) and using Oblivion's Gamebryo engine to render rather nice looking 3D environs. www.hiddenpath.com
People who love TD games should definately try and get Warcraft III, there are so many excellent TD maps for that game, and new ones are still popping up almost every day (although the quality varies wildly :)
Take a look at Elemental TD ([www.eletd.com]), which is one of the finest TD maps ever.