Today Microsoft has released an Icon Pack for developers building applications and games for Windows Phone 7 Series. If you are intended to code app for Windows Phone 7 Series, this pack is really worth for you.
Charlie Kindel says-
This package contains a set of 64 app bar icons that you can use when developing applications for Windows Phone. In addition to the 64 icons in PNG format (32 dark and 32 light), this package also contains vector versions that can be easily imported into Microsoft Expression Blend 4 Beta when using the Microsoft Expression Blend Add-in Preview for Windows Phone.
Courtesy: Windows Team Blog