For tarp tensioners I used old shock cord from a tent and it's worked just fine. The others are right though if there is a lot of tension on it you may want to go with new cord. It prevented my tie outs from pulling out also.
A lot of old tents have great material for stuff sacks and even zippers and bug netting that you can use. I trimmed off a gear loft from one tent and use it for a "quick get to compartment" type of pouch. It's really light, has a quality zipper and ties on my pack with those little fabric ties.
I took the old poles with the cord removed, glued and screwed together the sections and use them as connector rods for a pulsk type sled. It worked pretty good for zero cash outlay.