After a few months of beta testing, the release version of XNA Game Studio Express is finally available for download. Prospective game designers anywhere can get a year's subscription for $99, which allows them to make games on their Windows PCs and play them on their Xbox 360s.
The subscription also allows gamers to play other people's creations, which is likely what most people will be using this for. From what we hear, it's pretty easy to use as well. If you just want to try it out, there's also a 4 month version for $49.
Download Page [Microsoft]
Press Release [Microsoft]