Sears stores sell what is called an "Asia Phone Card", which appears to have the lowest per-minute rates to most countries in that part of the world (of course, there is a initial connection charge that is higher than the per-minute charge, but if you plan to stay on the phone awhile, you'll come out better, the long run).
Also, the calling cards you buy at Costco (Verizon) and Sam's Club (AT&T) offer great rates, too!