Feb. 15, 2010 — Mobile World Congress 2010, Microsoft Corporation CEO Steve Ballmer introduce the next generation of Windows Phones 7 Series. Microsoft will bring together Xbox LIVE games and the Zune music and video experience on a mobile phone, exclusively on Windows Phone 7 Series.
The Windows Phone gets a high-level overview of the new application platform and a complete picture of the developer story. Learn about the developer tools, the application frameworks, the support for Silverlight, and the support for XNA.
For developing Windows Phone 7 application development we will need the following components installed.
1. Expression Blend 4 Beta
2. Windows Phone Developer Tools
3. Microsoft Expression Blend Add-in Preview for Windows Phone
4. Microsoft Expression Blend SDK Preview for Windows Phone
Here is pre-release documentation click here
For developers help Windows Phone 7 forum
For More information about development see here
Windows Phone 7 Series Developer General FAQ
Thanks for you time :)