Secret Resource: Waterproofing! Answered
Everywhere I look, people are throwing out umbrellas. I've started scavenging the skins and (in rainy England) sewing them onto *everything*. It's great. There are tons of umbrellas that break, etc. and are thrown out every day. You can sew them together to make a big tarp, make a cover for your bag/laptop, etc. Wonderful!