I would get one of these:
Polyurethane-coated nylonmore durable, heavier (14 oz), cheaper ($22)
http://www.campmor.com/webapp/wcs/stores/servlet/ProductDisplay?productId=39295901Silicone-coated nylonless durable, lighter (8.5 oz), more expensive ($45)
http://www.campmor.com/webapp/wcs/stores/servlet/ProductDisplay?productId=9996340If hiking, the weight you're saving by not having a tent or separate tarp more than makes up for the extra 5 oz of the poly-coated nylon.
(I'm not affiliated with the manufacturers or campmor.com.)