Look in your own closet for 100% cotton clothing you aren't using. In addition, remember that 100% cotton sheets, some curtains, some shower curtains in good shape are also suitable quilting fabric sources in thrift shops (and at home) as well as men's shirts. Look for long sleeved larger sizes for the best bang for your buck. Thrift stores also run specials. I really enjoy recycling these type of fabrics into quilts like our grandmothers (and grandfathers) made. It's kind of neat to be quilting "green" and keeping those fabrics out of landfills while turning them into something warm and comfy.