Microsoft has released a software development kit for the Bing Maps WPF Control

This software development kit (SDK) provides the binaries and programming reference for the Bing Maps WPF Control (Beta). You can use this control to build your own applications that use Bing Maps.

Instructions
Download the installation file.
Run BingMapsWPFControlBetaInstaller.msi
Choose a location to install the Bing Maps WPF Control (Beta).
When the installation completes, you can choose to open the Bing Maps WPF Control (Beta) SDK help file (BingMapsWPFControlSDK.chm).

  Bing Maps WPF Control (Beta)