These stick together by magnetic force when not in use. The Magnito Salt & Pepper Shakers by Josh Owen for Kikkerland is a small set of shakers that you can keep track of by sticking them together at the shaking surfaces. The holes for the contents are in different locations, so when they're stuck to each other the salt and pepper don't mix and don't leak.
And, best of all, both shakers are shaped in such a way that they can be spun like tops if you feel like playing at the dinner table. The design was winner of the 2005 Good Design Award from The Chicago Athenaeum of Architecture and Design Competition.