Pulley post (quick idea for rainy days)

My sister and I used to play this all the time when we were little-take a piece of string and tie it in a loop around two chairs spaced far from each other. Write notes (or for younger ones, draw pictures), peg them onto the string and send them to each other by pulling. 

Doesn't cost a thing and kept my two (even my 20 month old) busy for most of the afternoon!