Overstock
I just recently learned that Overstock.com sells batting and interfacing and some other sewing and craft supplies. I just did a quick check but did not compare prices. It might be worth a check if you are in the market for anything along that line. I had posted a note looking for interfacing here and someone recommended them. She said it was where she got her interfacing. They didn't have what I needed but I was surprised at how much they did have.