I have made this circle quilt from the site that was posted. I begged old jeans from co workers and my sons' friends. I, (stupidly) took apart all the seams and then cut each 6 inch circle by hand. DH helped draw and cut circles. I then used 4 inch squares in the centers of the circles. I made it very large...400 six inch circles. :) Using denim is a really good way to "recycle" and makes for an extremely heavy quilt. I used denim needles and cotton thread. Good luck on your denim quilt and post pics of yours. (If you look at my avatar it is the denim quilt I made. Also, I have posted pics of mine on the board.)
P.S. I also cut the pockets out of Levi's and used them for the center of the quilt where the squares go. :D