From We Make Money Not Art blog:
littleBits is a growing library of preassembled circuit boards, made easy by tiny magnets. All logic and circuitry is pre-engineered, so you can play with electronics without knowing electronics. Tiny magnets act as connectors and enforce polarity, so you can’t put things in the wrong way. And all the schematics will be shared under an opensource license so you can download, upload, suggest new bits and hopefully see them come to life.
Very cool and fun.