Microsoft .NET Micro Framework Is Now Available: New platform allows developers to build embedded applications for smaller devices using .NET and Microsoft Visual Studio tools.

For times when size does matter 

The .NET Micro Framework grew out of the Smart Personal Objects Technology (SPOT) initiative at Microsoft. This framework is a natural extension of Microsoft’s offerings for creating embedded systems and provides an easy-to-use solution for this type of development. Though it is used on very small devices, the Microsoft .NET Micro Framework provides a managed code environment that brings a strong degree of efficiency and reliability to the realm of embedded software development. More information can be found at http://msdn.microsoft.com/embedded/netmf.

Source: Microsoft .NET Micro Framework Is Now Available: New platform allows developers to build embedded applications for smaller devices using .NET and Microsoft Visual Studio tools.