I have not been able to get a really white background with the cloth that we got at Jo-Ann Fabrics. So I asked my wife to pick up white poster board from Staples and I ordered white muslin photograph background. Here is a comparison shot using some paint cards from Home Depot. The white poster board seems to give the cleanest, brightest white, but I also like the softer white of the white muslin, I will try to play with both backgrounds in the next couple of days and post some of the results.
What have you guys used for your backgrounds?