3 Stages:
Phone Screen
Video Interview (they will give you software for the interview. Not skype)
Onsite Interview in Austin, TX (final interview)
They are very flexible with timeframes you set for interviews. Please utilize this and take your time to prep for it. I extended the time between my interviews for a while.
Recruiter will will give a 15 to 30 mins interview. My recruiter was friendly very helpful and even helped with a few similar questions of what they could give in the next stages. It helped a lot during the video interview, not at all in TX interview. Very positive exp with my recruiter and FB overall.
One more thing: Do not take the last interview for granted. Its actually hard. And its easy to take it for granted because the first 2 interviews are real easy. It's not all rosy out there !