The ones from Connecting Threads are nice. Also, if you're looking for the brand names at decent prices, Seawatch Fabrics has good prices and free shipping (and quick too) for orders over $30.
http://www.seawatchfabrics.com/
The ones from Joann's are nice, but overpriced at regular prices. Not bad if on sale or you have a coupon. But they don't have as much variety.