I started out with Polar Notions. They are nice, but pricey. After that I went with comic book boards. The are acid free and you can get 100 for $10. Overall I have to say I really prefer the comic book boards. They hold the fabric nicely and the big plus - they aren't as thick so you don't lose shelf space. It adds up when you start thinking about it. I thought about buying some of the other ideas mentioned but I just really didn't want to spend the time cutting them to size. This just works for me.