The Making Games in Collaboration for Learning (MAGICAL) project, in which we’re a partner, has just released an updated version of its list of game-making environments (pdf). It contains information about nearly forty different game-building tools, classified by cost, game-type, and type of access (i.e. online or download).
One thing that struck me is the lack of online tools for game-building. Given the practicalities of gaining access and installing software on most institutional computers, this is a real barrier to game-building in the classroom.