On August the 30th Microsoft will be releasing Beta 1 of XNA Studio Express that is a feature cut version of XNA Studio Professional so that anybody can make games for their PC using more centralised tools.
When the product is released later this year users will be able to pay Microsoft $99 to join the "Creators Club" which will probably have documentation and a forum for people who are trying to make games using XNA studio, but will also allow members to run their code directly on the XBox360.
The press release is Here
The language or languages that Microsoft will be supporting or providing documentation for has not yet been said, but to put a slight lid on a lot of the excitement people have been having today about the prospect of making games at home, game development up until now has only been done well by teams of dedicated individuals for a reason and although this centralises all the tools and skills necessary to produce a game I don't think it is going to make the task any smaller.