There's a ton of ripstop on the dollar table at my local Ben Franklin's, but I don't know how to tell if it's heavy enough for a hammock. Some of it seems thicker, and some of it just seems stiffer. They had some that is shiny and slippery, so I bought all of that just in case it is sil nylon. That's what you make tarps out of, right?
I'm a big feller (240 naked and with an empty bladder), so I want the strongest nylon that's reasonable to carry, but maybe some of the lighter ones are strong enough for my daughter.
I picked one that seemed to be stiffer than the rest but I'm not positive that it was any thicker, even though the lady that helped me said she thought it was thicker and heavier. I'm making a hammock for my wife with that, and I'm going to keep an eye out for something with a label on it for myself. It's white with a floral pattern, so she's happy with it.
They also have a ton of very thin ripstop thats dark green with a dark floral pattern. It looks like it would make a very effective camoflage. I'll probably buy a bunch of it to make a tent or even just a ground blind for hunting. This is also on the $1 clearance table.