Facebook came to my university's career fair and I briefly talked to one of their engineers and gave the recruiter my resume. They emailed me back within 1.5 weeks and invited me to do a 45 minute interview 1 week later on my school's campus. During the 45 minute on-campus interview, the interviewer asked me to briefly introduce myself and summarize a few highlights on my resume. Then he gave me a few simple coding questions to do on the whiteboard. He allowed me to use any language that I wanted to use. Also, the night before the campus interviews, Facebook hosted a reception at a pizza place so that all the interviewees could casually meet our interviewers beforehand. No need to dress up for a Facebook interview--they're very casual. My interview was wearing a t-shit.