Adam bought me a Christmas gift from the Museum of Modern Art. I don't know what the gift is, but the packing material is pretty neat. It's these little cylinders which are starch-based (presumably corn starch). We used a corn starch weed rug from Lee Valley this summer in the garden, and it held up remarkably well. After reading The Omnivore's Dilemma, I'm a little bit concerned with the mass growing of corn crops, (and more and more are being grown for ethanol now) but I think that these are still better than plastic. They can be reused, composted, or flushed. I think that's pretty versatile.
Here's the card that came in the box.
So I put some in a bowl of water, and waited.
Okay, so I couldn't just wait. I poked them a bit.
And after about a minute, they looked like this, and then they completely broke apart. So I swished them down the drain with some more water. Neat!