Over the Rainbow has a huge variety of designer fabrics and tends to be priced lower than most of the other shops out there.
http://www.overrainbow.com/cgi-bin/Store/store.cgi
Whittle's Fabrics has really low prices but a smaller variety.
http://www.whittlesfabrics.com/shop/
I find using both quiltshops.com and exploring new shops with the fabshophop.com helps to track fabric prices and varieties to be great fun.