Fun Electronics/Robotics Projects for Kids!

[rawfuls]

So basically, this is a little off of R/C topic, but cool nontheless.
We're hosting a little 'summer camp', aka a daycare but we influence them into robotics & whatnot.

Anyways, we're designating 2 hours per day (maybe 3) for cool projects they can either take home, or perform at school (by take home, I mean like take home and use too).

For example, a portable USB charger, they build it at school, and take it home & use! Kinda like a party favor!

anyways, we're kind out of ideas, so we're looking for more.
We're straying away from solder since we don't want 8-13 year olds soldering, but here's our list.

-Rubber band powered airplanes
-Air rockets (PVC contraption which reserves air to blasts up their PVC rocket)
-Water Squirt Gun (Pump, probably.. will probably be a little hard- out of PVC)
-Marshmallow Shooter (same as above, probably a pump, make out of PVC)
-Smoke bomb (Flint powder + chinese poppers + tape!)
-USB Desktop Cooling Fans (Reusing some old 120mm case computer fans from e-waste)
-LED Music Box (Connects to iPod, simple transistor makes LED flash to beats)
-LED Throwies (little throw-away LED lights, magnetic)
-Bristlebots (Those vibrating walking toothbrushes..)
-iPod Dock? (Maybe, most of them will have iPods anyways)

If you have an idea, please post! Anything will help!