One friend mentioned this: littleBits makes an opensource library of electronic modules that snap together with tiny magnets for prototyping, learning, and fun. Looks interesting. There are even instructions how to join littleBits to LEGO. All the modules are open source, check GitHub for Eagle boards and schematics for all the littleBits modules. The aim of littleBits is to bring electronics easily accessible to artists, makers, students and designers: Make circuits in seconds with the littleBits Base Kit—no soldering, programming or wiring required.