Crescent Moon came out with the innovative earth-friendly ECOmat for Pilates and yoga. It's made from patented TPE foam, so it contains no PVC, latex, rubber, or toxic materials.
Not only that, but it folds up. It sounds a bit odd, but the patterned grooves are said to provide superior traction. And the folds are fully enforced to prevent the absorption of sweat, so it's easy to keep clean.
It only weighs 2.8 lbs, and because it folds, it could be a great mat to travel with. You can get one for 49.99 in blue or green on the Crescent Moon website.