I love thousandsofbolts. And I love their cart where it tells you how many more yards you can add for the same shipping cost. Their shipping is unreasonably reasonable. I usually order a couple hundred $$ at a time, and their shipping only adds around .25 to .30 cents more per yard.
They are also very quick to let you know if they're short on something and ask if you still want the fabric. I recently elected to take a fabric even though it was 1 yard short of what I ordered. My refund was processed within hours, not days.
I also love fabric.com and I especially love their free shipping.
equilter is nice, but their shipping is high, imo.