First stage: Phone screen from the recruiter. Typical questions about my experience, nothing unexpected or difficult. I was immediately invited to come to an in-person interview.
Second stage: In-person interview with two interviewers. When I walked into the office, I noticed that the other employees didn't seems particularly happy or friendly. It felt like a tense environment. The questions I was asked during my interview weren't particularly hard, but one of the interviewers was very intense and stern - truthfully it felt more likely an interrogation than an interview.
Third stage: After my interview, I was asked to put together a report based on some data files they sent me. I put a lot of effort into it and sent it to them as requested at 11am. I didn't get any kind of response, so I emailed them at 5pm to ensure it was received. I got a one line response saying they received it, but with basically no other recognition.
They then asked for my references, which I provided...and then I never heard back from them. I found it extremely unprofessional that they would not call me to tell me that they were not giving me an offer. I ended up getting a job at a much better company, and after going through other interviews, I realized how pathetic this experience was, and how poorly they treated me. I've very glad I didn't get an offer - the interview process gave me a very bad impression of the company.