I love fabric.com! I order from them constantly. TOO often, really. That "new arrivals" link is just too tempting!
When they've been out of a fabric I've ordered they send me an email and ask if I want to cancel or proceed. One time they told me they were out of something that I ordered a 1yd cut of. I told them to go ahead and send everything else - when I got my box they had somehow found two half-yard cuts of the fabric they were out of, which they included in my order but did not charge me for. I liked that!
I've also realized that if I put a bunch of stuff in my cart but don't check out....in 3-4 days I get a 15% off coupon to motivate me to finish the order. Woohoo!!