They came to my school for a career fair, invited me to an on-campus interview. WIthin two weeks they invited me to the second round of interviews at their main campus. There was a pre-interview dinner at a hotel the night before, where we got a chance to meet other students and the Progressive recruiters and interviewers. They gave a nice presentation about Progressive and answered any questions we had about the interview process.
The next day (interview day), we showed up at 8:00 am and went through a rigorous day including three interviews, tours of the "campus," and presentations by former interns. The day concluded around 5:00 pm.
While they did not extend an offer for about six weeks, somebody called or emailed me at least once a week from weeks 3-6, updating me about the process.