The Urban Homestead, which also has all sorts of tidbits for satisfying projects.
All you need is a glass container, some flour and some warm water. You start with a cup of flour and a cup of warm water. All you do is mix until smooth and place it in a spot where it will keep warm-ish. Then each day you pour out one cup of the mix and replace it with a 1/2 cup flour and a 1/2 cup warm water, mix until smooth. The first day, nothing really happens, but from the second day on this bubbly goo smells like Miller Valley on a warm summer day. Keep doing it until you have reached day 14 and apparently, you can use it to make bread. I'll let you know how it goes.