Mont bell waterproof bivy/sleeping bag cover. Very light bivy - compresses super small.
Used less than ten nights - great condition. ~8.3oz in weight. I've not experienced heavy rain in it to validate the waterproof claims in full. But in the two nights of medium rain I used it in, there were no problems besides some light condensation inside. Pretty normal for a waterproof bivy with the opening basically closed all night.
Review:
http://www.backpacker.com/august-2010-gear-review-montbell-breeze-dry-tec-ul-sleeping-bag-cover-bivy/survival/14360Retail is $155 for the wide and long. I'm 6' and 195 - plenty of space for me. Dimensions are 98.5" x 37" with a draw cord that opens wide for easy entry/exit after minimal practice. Shipping is a flat $5 - Continental US.