I have several favorite online shops, but only a few that I have purchased from and some of those have been due to winning a gift certificate through FabShop Hops.
Anyhow, two favorites, that I have purchased from and have received quality product, fair pricing, fair shipping and good customer service are
http://www.overrainbow.com located in Washington state, they are who I regularly order from. I always start here, there are great sales and she has a really unique newsletter.
http://www.sewnatural.net located in Kansas, they have excellent customer service, you won't be disappointed.