You can get very nice fabrics and good prices from many places. Thousands of Bolts and Quilt Fabric Closeouts are a good place to start. The fabric is first quality, just not always the most recent releases. Both are quick to ship and have great customer service. Many places will have clearance sections also. For that, I like to check out the shops on Quiltshops.com
http://www.thousandsofbolts.com/
http://www.quiltfabriccloseouts.com/
http://www.quiltshops.com/index.html