I was contacted by email after visiting the Amazon booth at my university's Career Fair, and a recruiter set up an on-campus interview.
My first interviewer was very chill, but was almost plodding in his need for detail. Another peculiar technique was to ask for a solution, and when I gave him one, ask for another and another and another and another, until I was giving less and less efficient solutions. He wanted me to admit that some of the naive solutions would be faster to implement than my initial optimal solutions, and therefore valuable when you want to get a feature out there immediately and scale it up later. Then, he had me code on a piece of paper, and was very picky about syntax. I received a phone call from him about an hour later, congratulating me and setting up three more on-campus interviews for two days later.
My second interviewer was also pretty chill. He started out by enthusiastically describing the challenges of optimal shipping. He had me code up a couple problems on the white board, and seemed surprised by my use of bitwise operators.
My third interviewer was the most senior. He had me design a chess game, and implement several of the key classes and methods. He also asked me some behavior questions relating to my past experiences with group coding projects.
My final interviewer had to have been the bar-raiser. He was a short dude with a very intense stare. As soon as I walked over to his cubicle, he informed me that he "had been listening to [my] last interview through the wall". I was kind of weirded out, but relieved that I hadn't screwed up the last one. The final interviewer asked me some more behavioral questions, and had me code up a LRU cache. I hadn't done that problem before, so it was fun working up to the optimal solution.
A week later, I got an email congratulating me and asking to set up a phone call to discuss the offer. They also invited me to Amazon headquarters to stay for three nights, meet all the teams, and hang out in Seattle for the weekend. I haven't decided whether to accept the offer, but I am looking forward to the visit!