As I researched options for a SIM card for three weeks in China, this option appeared:
http://www.bj.chinamobile.com/www/ac.../introduce.jsp
That's for foreigners, pick up at the airport and starts at RMB 218 for 200 airtime credit and - if I read it right - 5 GB of GPRS traffic. That looks like a good fit for my needs.
I also stumbled across a new "12593" prefix for calls to the USA. One of the China hands may know more - is this IP or discounted circuit?