i shop by price and typically that means fabric.com (coupons and free shipping), thousands of bolts, quilt fabric closeout, whittles, etc.
if i'm going to pay $8-$11 a yard for fabric online (basically retail but still cheaper then local) i use equilter because they donate money to a charity of your choice from a list.
i figure if they all have that price might as well give it to the online company that does outreach work.