I always do it by Bank of China-New York Branch or Bank of China -Chinatown branch, NY. Ask your parents to open an account in a branch of Bank of China in your hometown (using Renminbi is OK), and then you can ask Bank of China to send your money to your parents' account in China. It is usually takes two to three weeks for your parents to get the money. But if you use wire-transfer, your parents can get the money within one day (you need to pay more fee in this case). See the following website for more details:
http://www.bocusa.com/page/pb/forms.shtm