Cali Quilt Co on Etsy is my favorite, great mom & pop shop with super fast shipping and wonderful customer service, I've been a regular for years (they used to be called Stitch Stash Diva)
I like Fabric.com as well, it seems for me like their shipping takes forever which used to drive me crazy but on the last 3 orders they've given me the last almost yard off the bolt for free (I ordered 1 yard and they sent me 1.75 yards) and they did it twice in all 3 orders.