Try www.thousandsofbolts.com/ If the fabric on any site is not manufactured in the US, then you may get charged customs duties. It seems to be hit or miss; however, I have found that priority post envelopes (which contain 6-8 yards of fabric, depending upon the seller) cost about $12.00 and rarely incur customs charges. If you order more, it comes in a box which seems to attract more attention.
I get on mailing lists so that I am notified of sales by email. eg. www.hancocks-paducah.com/SubCategory--WEB-SALE-FABRIC--m-62 - (note: they sell by the 1/2 yard)
www.batiksplus.com/ has a sale right now. They have many batiks that are unavailable most other places, such as older Hoffman designs. They are also a great place to get McKenna Ryan fabrics.
This shop in Chilliwack, BC always has fabrics on sale and once in a while will have a deal for free shipping, which can really make it worthwhile to order from them. www.hamelsfabrics.com/ Once again, get on the mailing list so you are notified of sales.
When most US sites say, "free shipping", the offer only applies to the continental US. The $7.00 shipping charge at fabric.com is a great deal. If you have friends who spend holiday time in warmer places south of the border, you could have orders sent to them. If they drive back and forth, it's usually not a problem for people to bring a couple of parcels back with them.