Microsoft .NET Gadgeteer is an open-source toolkit for building small electronic devices using the .NET Micro Framework and Visual Studio or Visual C# Express (the free C# development environment). Gadgeteer combines the advantages of object-oriented programming, solderless assembly of electronics with a kit of peripherals, and support for quick physical 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. Microsoft .NET Gadgeteer has been developed by Microsoft Research in collaboration with the .NET Micro Framework product team. In this demo, we will provide an overview of the various hardware and software elements of the .NET Gadgeteer platform. Moreover, we will present a wide range of showcase projects that relate to our work in research and education and demonstrate the design of custom enclosures.