Two interviews, one with the Director of HR, one with the Account VP. I was previously known to the onsite contract lead so that wasn't an issue for me, but if you're coming in fresh you will have to talk to them as well. The work culture is a little ossified (no jeans on Fridays, no telecommuting regardless of the client's preferences) and there are the typical pitfalls of working with a small company that depends mainly on one large client.
If you can speak intelligently about the kind of work you do and a couple of awesome things you've accomplished, you're in like Flynn. There are no trick questions or obnoxious Microsoft-type brain teasers.