Microsoft .NET Gadgeteer

Microsoft .NET Gadgeteer is an open-source toolkit for building small electronic devices using the .NET Micro Framework and Visual Studio/Visual C# Express. Gadgeteer combines the advantages of object-oriented programming, solderless Assembly of Electronics with a kit of peripherals, and support for quick form-Factor construction using computer-aided design. This powerful Combination allows embedded and handheld devices to be iteratively designed, built and programmed in a matter of hours rather than days or weeks. Here is a video description of the platform.