Phone screen with an internal recruiter, followed by a semi-technical phone interview with the lead developer, then flown to their headquarters for in-person interviews. I was interviewed by 5 different people over the course of the day. The people I interviewed with were developers on the team I was interviewing for, developers on other teams, and an engineering manager.
Everyone was really nice and professional. I loved the team and the opportunity, but ultimately I had to decline due to the offer not working for my specific circumstances.