Poll: http://www.mojang.com/2012/02/15/humble-bundle-mojam/
The genre is going to be RTS and shoot 'em up combined! And the theme is going to be a mix of Steampunk and Ancient Egypt!
Also, for any avid game designers (or anyone interested in the game), they are going to stream the entire 60 hrs of their game creation marathon on twitch.tv!
Trailers:
The game will be sold as a humble bundle, which means that you can pay however much you want, and select which charities receive what amount of money. I'm not sure, but I think you have to buy the game before it finishes.
http://www.humblebundle.com/
Stream here: www.twitch.tv/mojang
Personally I'm quite excited about this. While I haven't played minecraft, I've heard alot about it. Being a fan of RTS and shmups I'd love to see what sort of crazy touhoucraft they could come up with.