1. Helix Navigation Framework
    Helix is a simple route-based navigation framework for Silverlight and WPF. You can read about Helix here.
  2. Prism Template Pack
    Prism is a Patterns & Practices application block for building loosely coupled, modular client application in Silverlight and WPF. You can read about Prism here.
    The Prism Template Pack provides a set of Visual Studio solution and project templates to speed up your Prism development. You can read about the Prism Template Pack here.
    Note: Be sure to remove the .zip file extension once you've downloaded the template pack (so that it has a .vsix file extension).
  3. Prism Tabbed Interface Sample
    A Prism sample showing how to implement a tabbed view interface (similar to Visual Studio), as described here.