Green Screen Fabrics

I aint buying one myself it is my partner but I was helping her look for one :) I will let you know what she goes for.

Yeah Micheal, what lion said, the color in fact doesn't matter too much any more tbh. Most programs will chroma key out any color, and many people have two different color screen in case they want to wear that color during the video. However, the darker the fabric the more it becomes like other darker colors, and while a strong program chroma keys out by color lengths (i.e. if any green is found to be dominant it gets the boot =p) weaker programs may not have this effect and rely solely on visible color, in which case the brightest most eye burning green you can find would be great =]
the best kind of green screen material is muslin, although any green material will work to a certain degree. Muslin works the best because it's the LEAST reflective and has less green spill than most other fabrics. I got the green screen that I use at tube, and it has worked great for me thus far. You want a material that doesn't reflect light back on to your actor or whatever your screening.
Just that bright dayglow greeen green stuff works fine, go to your local fabric store and buy it.

If you wanted the cheapest DIY ever you can use the neon green posterboard as well. Both are suitable for small projects or experiments but not what I would permanently invest in if you plan to use green screen on a regular basis.
The idea with a green screen is to have a color that doesn't occur very often in skin tones, etc. That is why a brighter green is a better candidate. However, more important than the shade is the evenness of the color.... meaning that even lighting is vital. A felt green actually works pretty well as it doesn't get shiny spots as easily. In my studio, we have a giant green screen that is a felt-like material, and it's the best one I've used (other than in a real green screen studio).