There's a few of these projects going on, which involve filling a page in a notebook with doodles, words or anything you like and then posting it on to someone else across the globe.
From the site:
‘Do Not Leave Unattended!,’ allow(s) you to write, draw, create a collage, or whatever method you choose for recording your contribution in a notebook to be shared with the rest of us. 10 initial notebooks were sent out to the first participants in St. Louis, Los Angeles, Greensboro, Orlando, Brooklyn, San Francisco, Madison, Houston and Atlanta, with over twenty more put into circulation since the project kicked off in August of 2008.
So I have signed up, although it looks like the list is fairly long so I'm not sure as yet when mine will arrive. Quite excited about seeing what other people have done though, as well as adding my own little contribution! To see more or sign up yourself visit the site here.