Hey cayenne,
I just made myself a smallish (2m x 3m) one for playing with. It was from a fabirc store and the fabric type is called 'theatrical broadcloth'. It's pretty light and usually used in theaters (hence the name). Comes in many many colours. They had a few shades of green, so I used an iPhone app called ColorAssist which reports real-time RGB values to find the shade with the strongest 'mostly green' value. Clearly light can have an effect on the hue, so I also used the phone's LED and a flashlight I brought with to compare. Hadn't tried, but I gather taking a DLSR image of the same and checking the RGB histo could be a substitute (large green, small blue/red). The fabric came in 1m wide rolls (was like $3/m), so I bought 6m x 1m, and sewed it together to make 2x3m If you can find it the width you need without needing a seam, that'd be best. I rolled it onto a cardboard tube from the fabric store for storage. $20 and about an 30 minutes messing with a sewing machine.
I considered making a backdrop stand, but found the Manfrotto 314B kit to be worthwhile. I just slide the cardboard tube onto the crossbar, and I'm set. I could have made one cheaper, but the background stand uses standard light stands I can use separately, and it collapses very compactly, something a (at least my) DIY wouldn't have done nearly as well.
I did peruse the interweebs looking for info like you did, and mostly came up with muslin dying instructions and flimsy PVC stands or mondo 2x4 versions, hence the non-DIY stand. Commercial green-screen drops weren't cost effective to me, but the stand was.
With my initial quick testing (no production shooting yet), I could key it out quite well. Keep in mind the colour only matters in that it should be a colour that isn't part of the scene in front. Green is typically used as it is considered an 'unnatural' and unlikely colour (at least for people) , but if you're shooting a subject that actually has that colour (or close to it), a different (the farthest complementary) hue 'chroma key' backdrop would work better, as long as it's bright and saturated. I use Final Cut, and it has a 'chroma key' filter. All I do is dropper the background (to select the colour) , and mess with the width and saturation sliders, and poof -- no more background. The more evenly you can hang it, and more evenly you can light it, the easier and more selective you can make your key filter -- reduces the chance that you'll accidentally key out part of your subject.
