Stencyl (Java-based) is a new game development tool which allows games to be made with very little effort spent on programming. As described by the team:

Stencyl is a universal platform for tile-based game creation with an emphasis on user-friendliness and adaptability to many different genres. In other words, it's a tool that lets you create practically any standard kind of 2D game in existence.

StencylWorks, the game builder for Stencyl, is the tool that you'll be using to create games. It will be unveiled later this year.

3D games are not supported, but all creations made using this open source freeware development tool will run on Mac and Linux as well. I'm skeptical, but a lot of promises were made and if the developers keep their word then it could possibly rival Mark Overmar's popular Game Maker.