I have only bought from 3 so far, but they all were great.

Quilter Studio, Craft Connection, and The Quilting Place.

I had to send a money order because I don't have credit cards, and two of them sent out my fabric before they even had a chance to get my payment. I got exactly what I had ordered, and it came fast.

Thousands of bolts
Connecting Threads
Jhittle.com

Those are my favourites. I know I will find more as time goes on!

I shop at most of those mentioned but you missed http://quiltinaday.com
It has an extensive sale area with great prices.

i also like designsbysick.com and nixiechicks.com

I shop online for fabric 90% of th etime. Here are a few I use:
equilters.com
fabric.com
favoritefabrics.com
jandofabrics
hayloft fabrics
bugfabric.com
thespiderswebfabricshop.com
quiltscapes.com

I'm a HUGE Fabric.com shopper, too, but it's actually free shipping over $35, not $40. Not only are their prices terrific, but the fabric is top rate AND they are incredibly helpful!

I recently bought fabric at crowsnestquiltingfabric on ebay, I think Butterflywing on this forum recomended it. Great fabric and you can't beat the prices. I was very pleased with the fast service too.

All great places to shop.