Make a really really big pinhole camera. I used the box my computer came in (a holstien looking thing) and make paper negatives.

Box---free

Blackboard paint for the inside of the box---$5 or so.

Pinhole---make yourself out of shim stock or buy a readymade

Shutter---a chip of wood and a thingamabobble to keep it in place, you've probably got something you can use in your garage or junk drawer.

Printing paper---whatever 16x20 RC Freestyle has on sale.

Trays for developing---if you haven't got large ones, those black plastic tubs used for mixing mortar are worth looking at (the hardware store sells 'em)

Light meter---why bother?

Cheaper than a set of golf clubs!

Have FUN!
BEWARE! Highly addictive!