I purchase redwell folders. They come in letter and legal size, expand to about 5", and fit great on a shelf. I put all the fabric and the pattern in it, so the fabric doesn't accidentally get used in another project. I can work on something, place all the pieces, blocks, fabric & pattern back in the folder and put it on the shelf. If I purchase a kit, I put it in a folder, even though it's already in a package. That way, if I start it, I have somewhere to put all the pieces. And if I purchase the backing and binding fabrics, I can keep them with the rest of the kit.
The redwell folders also make great magazine holders. I have one for each of the mags I subscribe to.