I just stumbled across Kevin Kelly — Recomendo (via McGee’s Musings), and his most recent recommendation is Simon Field’s Science Toys You Can Make With Your Kids:
Probably the coolest source of educational science demonstrations I’ve encountered is this very book-like website written and run by Simon Field. Field has 30 nifty toys and gadgets that can be made quickly, cheaply and will amaze adults as well as kids. This is the only place I’ve seen that tells you how to make a magnetic linear accelerator, also known as a Gauss Rifle — it uses magnetism to shoot tiny steel balls…
The whole list is interesting though. For instance, once you see some Griptwists, you know you need a few.