I applied online. The process took 4 weeks. I interviewed at SpaceX (Hawthorne, CA) in Dec 2012
Interview
Applied through their website and was contacted a few weeks later for an interview. You will meet at the site with a large group, but the interview is one-on-one. You will most likely only have 10 minutes or less to "sell yourself" because the person interviewing you needs to get back to work. Some are very nice, most just want to get it over with.
Interview questions [1]
Question 1
If you are interviewing for a specific department, KNOW what you're talking about. Meaning, if you just made something up so that it will look good on your resume, RESEARCH IT. They will ask you about every detail and every job you list on your resume so be prepared to back it up.