I was first contacted with a recruiter. She went through a basic (to my mind) skills test as a sort of front-end filter to make sure that my qualifications really were in line with what was being looked for. This was done over the phone. After this, an actual phone interview was scheduled with an engineer.
The phone interview got very technical, very quickly, with the interviewer feeding me many scenarios relevant to Google's situation as a provider of massively distributed services. He was not looking for me to guess how they did it or give any particular "correct" answer, but was looking to see how I arrived at *workable* answers. I liked this approach.
I was then flown out to the Googleplex for a one-day, all-day interview with about 6 different people, each of whom got about an hour of my time, with a lunch hour in the middle. The interviews covered algorithms, software engineering, project management, team management, and so on. All of them were, in their own way, quite technical, and all of them focused heavily on questions that posed a problem and asked you to solve it. Again, they were looking for *how* you solved problems as much as for solutions themselves.
I'd read many interviews of this process ahead of time, so I knew pretty much to expect all of this. I was glad I had done so, however. Some past reviewers had really not expected this sort of academic-oral-exam style of interview, and didn't like it much at all. I was fine with it, despite the outcome, because I knew it was coming and because I actually liked the approach.
In the end, I was not hired. I was not told exactly why not, only that the group of people who had interviewed me had chosen not to proceed. My speculation is that either I did not have enough actual management experience in my background for what they were looking for, or that one or more of the interviewers simply didn't think I was up to the job. I bear no grudges, as I knew the job was a bit of a stretch for me. It would have been cool to get, but as it is, I got a glimpse into one of the cooler companies making things happen on the web.