scitoys.com has very nice DIY electronics.

http://scitoys.com/scitoys/scitoys/magnets/gauss.html

->o  Moo  Moo  Moo  Moo
   ----------------------

Nothing to do with cows.
M is a magnet.
o is a metal marble.
-------- is a ruler with a groove.
The whole is a gauss gun.

Make a REALLY BASIC motor: http://sci-toys.com/scitoys/scitoys/electro/electro.html#motor