Async Targeting Pack for Visual Studio 2012
If async keyword is one of your wishing list for birthday, then you can strike this wish out.
Async Targeting Pack for Visual Studio 2012 will give you the option to use C# 5.0 language features when targeting VS 2012 into .Net 4.0 or Silverlight 5.0.
wanna learn more about async? Go here (and watch Stephan Toub).