On a podcast the other day one of the members was a little upset that a Windows Phone 7 Series SDK isn't yet available. While the SDK will be welcomed I'm not completly convinced that its curreny lack of availability is a road block for developers
XNA Game Studio 3.1 is available right now and if you download it you can start getting used to the SDK on your PC. If you have a ZuneHD or an Xbox 360 you can use those too. The SDK is really easy to use. You can grab it from http://creators.xna.com
While you are at it check out the 800+ games that are currently available that were written in XNA. There are some pretty cool looking games in the catalogue.
Tags: XNA, Windows Phone