One of my favorites is Thousands of Bolts (www.thousandsofbolts.com/index.cfm). They ship international and prices start at $3.95 a yard. They also have a color matcher that is really helpful. All the fabric is first quality name brand. I've been very happy with everthing I've gotten from them.
Also try Desperate Quilters(www.desperatequilters.com/). Some sale as low as $3.00 a yard.
Some US fabric sites on-line quote prices for 1/2 yard instead of 1 yard so you need to watch out for that. I've made that mistake a few times.
Good Luck!