Spec# has been released and I though it should be of interest for the group:

http://research.microsoft.com/research/downloads/Details/f96c1618-b332-4106-b0fc-911346d5f537/Details.aspx

Spec# is an experimental language that extends C# with several design-by-contract features. The new features of Spec# include a non-null type system, method pre- and post-conditions, loop invariants, and object invariants. The Spec# Programming System provides design-time checking, run-time checking, and a static verifier. This version of Spec# runs on .NET Framework version 2.

Particularly interesting for me: The non-null type and Loop invariants.