Found this interesting post on eco-yoga mats: http://www.idealbite.com/tiplibrary/archives/total_poser/
I plan on buying eco yoga mats the next time I make a bulk purchase, and I thought this was a great resource with a list of sources for eco yoga mats. When I do replace my mats, I don't want to just toss them, and it has a great link to ideas for reusing old yoga mats. The best idea for teaching was to cut up old yoga mats to make shapes and letters for kids games or stamps. You can use cookie cutters and an xacto knife, or just freehand it! For older kids, they could make their own stamps.
Here's a link to all sorts of cookie cutters to choose from: