Backgrounds and Backdrops for Photography
A list of popular Background and Backdrop vendors for photography.
For raw muslins, some dyed ones and some canvas, check out http://chicagocanvas.com.
For painted canvas check out Silverlake.
Silverlake also has a forum where you can talk to the owner (Travis) and other people that are using the backgrounds, plus talk about photography in general.
Finally, don’t forget to check out Steve Kaeser for both types and even Backdrop support systems. They have one system that includes Black and White Muslin along with the support stand.