Most of the numbers in the replies are on target. The MGMA and AMGA salary surveys are pretty accurate. Keep in mind that there are big regional differences. Docs in San Francisco make peanuts. Docs in the Southeast do much better. Denver is another area that has poor pay. It basically boils down to supply and demand. Popular places with lots of training programs don't pay well.
As far as REI goes, my wife had a starting salary of $200,000. She quit that practice because it sucked and the person who ran it was running it into the ground. You can check out my blog on starting a fertility practice. From the numbers we have been running, a RE doc who owns their own clinic can make around $500k, but it is a business and chews up lots of time.
Docs who work for Integramed make around $400k. They do not have the business hassles, so they make somewhat less. They do work reasonably hard, but there is still minimal night work.
We know some people who work for Sher, and they start around $200k and work up to around $350 or so. Kaiser is about the same.
For MFM, you can do pretty well. With our population getting more obese and having more medical problems, as well as waiting longer to start families, their services are in big demand. All those ultrasounds add up. My wife refers many pts to a MFM here in town who is doing quite well. The $350-400 numbers are probably on the low side. I would say those are for an employed MFM. If you own your own practice and run it right, you can do better.