Here are some interesting and useful things to do with toilet paper rolls (okay, one of them was just silly and the last one was rather crude, but a number of them showed promise).
Here's one of those ideas put to use. The toilet paper roll seed pot idea has been circulating for awhile, but...what a great idea! I've also seen people cutting and folding layers of newspaper to create a seed pot. I would think that both probably result in seed pots that will readily break down once planted in the soil.
On the creative front, another person took a toilet paper roll, put it on a paint roller (their friend used a lint roller) and affixed foam cutouts to create a roller stamp.