I submitted my resume to an on-campus recruiter and received an email that same evening. The recruiter wanted to chat on the phone 2 days later, which was was a quick discussion of my background and interests. At the end of the call I was invited to attend a half-day of on-site interviews just 3 days later (after the weekend).
The on-site interviews consisted of 4 separate 45 minute 1 on 1 interviews with 4 different Microsoft developers. They asked typical technical design and algorithms questions, and also wanted to spend a lot of time hearing me talk about a project I had worked on in the past. The first interview was very straightforward, but they become progressively more difficult. In later interviews they specifically ask you about topics that your resume indicates you have no experience with, to see how you handle unknown situations.
Results were given on the spot by HR, so less than 5 days after first getting in touch with Microsoft a job offer was on the table. Overall an extremely efficient interview process. They are clearly pushing to hire early before top grads get snapped up by their competitors.