Knit or crochet with plastic bags

http://www.pieandcoffee.org/2005/11/17/how-to-knit-a-plastic-bag/

I haven’t tried this yet, but it looks like a good idea.

Or you could use cassette tape.
http://www.girlontherocks.com/knit/blog/2006/11/07/tape-case/

neato! wonder how sturdy they’d be as hammocks.

a whole bunch would make a snug sleeping place. just mind the fire & ventilation shafts.

I sort of get shivers down my spine imagining the horrendous squeaking sound that knitted cassette tape tape might make. . . especially in a hammock situation where it gets slowly stretched. . .aaaaaaaaaggggh!

One could then iron the result between layers of cloth to make a very strong tarp.