I've had a couple of large orders through Connecting Threads & have been totally satisfied. I've also ordered from Fat Quarter Shop, good transaction there.
And recently I've placed an order through Hawthorne Threads which I haven't rec'd yet. They have a basic shipping rate of $4.50 for up to 2yds of fabric, but it's surface shipping I believe, no bells/whistles. You can get details on their site.
You really have to do a careful read of the shipping costs & then calculate if it's a good buy compared to getting merchandise from your local quilt shop.
Sometimes I feel like it's comparable or maybe a wee bit pricey but often it's the fabric design I'm after that I can't get locally.
Maureen