Also, I found this site:
http://www.extremtextil.de/They sell cordura, merino wool, fleece, softshell, etc by the meter, straps, buckles, grommets, and so on.
And while they're from Germany, they ship in the EU and apparently worldwide as well.
They also have a gallery for stuff their customers made. I'll dump some images from there.
This is a silnylon tarp.
I really want to make a tent supported by just trekking poles, but I'm not sure how feasible that is for 3 people.