The .NET Micro Framework let's you code with C# and run it on embedded hardware. This is really cool as it brings the .NET world and a familiar set of libraries to the developers.

http://www.microsoft.com/netmf/default.mspx
From the Microsoft .NET Micro Framework site
"The .NET Micro Framework is an innovative development and execution environment for resource-constrained devices.
It brings the same modern computing models that have proven to increase productivity on the desktop to small, intelligent devices.
In solutions where small devices are integrated with other devices and even the cloud, you can now use the same programming skills and code throughout the solution.
Its fully integrated Visual Studio experience brings a reliable and productive development system to the embedded world."