How much money can my wife, who is a permanent resident alien, and I, a U.S. citizen, send to my wife's sister who is a Chinese citizen without being subjected to the gift tax?

$13,000 in a year. Both of you can separately send $13,000 to the same person. Your U.S. Tax Return: The U.S. Gift Tax (http://taxipay.blogspot.com/2008/03/us-gift-tax.html)