Today, I created a covered backyard area, using tarps and PVC tentpoles.
I attatched the tarps to the backyard awning for the house using eyehole screws and short bungees that hooked into the grommets of the tarp. The other corners (and center) were supported with PVC tentpoles.
In the past at Burning Man, I've seen all sorts of PVC structires, but I haven't seen someone make PVC tentpoles quite like I did for this project. I bought relatively thick PVC piping, as well as one endcap for each piece of PVC. I drilled holes in the center of the endcaps, then put 3 1/2" bolts (the kind with threading running the entire length of the bolt) through them, pointing up. I then attached the bolts to the endcaps with nuts -- I would recommend using a washer as well, to reduce "wiggle". To finish the tent poles, just stick the endcaps on the PVC pipes.
What this gives you are strong yet slightly flexible tent poles with metal rods on the top of them -- essentially the same quality of tent poles that the army uses for large army tents. Of course, my solution only costs you about $2.50 a pole. These poles will support a large tarp structure with ease, even in heavy rain. Simply run the rod on your tentpole through the grommets of your tarp to attach.
To support these tent poles themselves, pound in a round tent stake, and slip the pvc pipe over the stake. That should support this kind of tent pole in most conditions, but you will probably want additional tension and support at the top of the pole to keep your tarp as taut as posible. Rather than having to mess with some kind of PVC frame construction, simply wrap rope around the rod at the top of your tent pole and tie it off to something, such as tent stakes. If you do tie it off to tent stakes, it is usually best to use two stakes spaced several feet apart, as that will provide additional tautness and support from all directions. A taut, somewhat slanted tarp will help you if it rains, as it will allow the water to run off effectively. Slanted tarps are also more likely to survive in windy conditions.
I still have to work on creating tarp "walls" so that I can keep the interior space warm, but it's getting there, and the mirror ball is in place. Next time around, putting this thing up will be a piece of cake!