Take a look at the electronic brick idea. There's a selection at iTead as well as other places scattered around the web. My favorite place to look at this kind of thing is at the YourDuino store (it's operated by one of the forum members) at:
http://imall.iteadstudio.com/prototyping/electronic-brick.html
ITead's stuff is here:
http://imall.iteadstudio.com/prototyping/electronic-brick.html