Shilad giving his final thesis defense on Thursday morning. (He passed.) This will be me in about a year.
An interesting tidbit is the variation in the Q&A rigor. A thesis defense has three phases, mandated by the Graduate School: (1) scholarly talk describing the thesis research, (2) public Q&A session, (3) private Q&A session. For Part 3, the public is dismissed and the professors get to ask the really hard questions. In my department (computer science), this phase is fairly cursory and lasts 10-15 minutes. In neuroscience, it's a grueling ordeal lasting two hours or more.
(Almost no one fails the thesis defense. If your advisor is halfway competent, he or she will not allow you to take it unless he/she is confident you will pass.)
Project 100, #52.