Microsoft is pretty committed to the consistent look and feel of Windows Phone 7, going so far as to releasing a huge 69 page Design and Interaction Guide. To make it even easier for developers to maintain a consistent look and feel they have now released a 64 icon application bar icon set.
The package contains a set of 64 app bar icons in PNG format (32 dark and 32 light), and 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.
For more information on how to use these icons within your application, see How to: Add an Application Bar to Your Application on MSDN.
The Icon set can be downloaded here.
Via the WindowsTeamBlog.