I had an empty cereal box and wanted to make something fun for my son. I googled "cereal box crafts" and found this post on another blog http://frugalfun4boys.com/2010/10/05/cereal-box-parking-garage/
(I guess she got it from familyfun.com)
I actually just looked at the pictures and made up my own. I didn't have toilet paper rolls so I just made tubes out of cardstock. It probably doesn't look as presentable as I'd wish, but my 3 year-old doesn't mind. :) He's having fun so far!