The Chinese government sets a maximum for domestic airline ticket prices based on route and distance, and guidelines for how much airlines can discount from that. If you use global websites you will almost always be charged the full-fare, which is flexible to change but quite expensive. Discounts on Air China have started to show on global websites but not nearly as low as on tickets bought within China.
Instead book on either ctrip or eLong (owned by Expedia, make sure to go to eLong, not the redirect to Expedia), both will quote virtually the same prices and be significantly less than global sites. Each prices the lowest fare but if you want more flexibility, each flight has an option to see the different fare classes with explanations of the fare rules. It used to be a pain to use foreign credit cards on these sites, but those issues have mostly been resolved. The Rapid Traveler has used both extensively and has no complaints.
Travelzen is a relatively new player and can be used as a backup.
These sites also cover hotels and tours. There are few stupendous deals for global chain hotels, but there is greater selection and information on local hotels, so worth a check.