when I go in the junk shops I look for large skirts that are cotton or large dresses. They can cut up into a nice size piece of fabric. I also check out the bedding. I have found lap size throws that are one piece of cotton print. Sheets are great for backings on a quilt or for piecing if the sheet is 100% cotton. Larger size blouses can be a source too of good piecing cotton fabric. Also watch for the sales they post. Our Good Will will mark stuff down on certain days.