Is anybody out there? This lecture reviews the ideas behind SETI, the Search for Extra-Terrestrial Intelligence, an effort to find other intelligent communicating civilizations by tuning in on their radio or other electromagnetic communications. I will discuss the basic approaches being taken by various SETI efforts, and what we expect to find. In addition to listening, we have also been broadcasting, intentionally or otherwise, messages into space, and we have sent physical artifacts with descriptions of our home on robotic spacecraft headed out of our solar system into interstellar space. Recorded live on 2009 Nov 24 in Room 1005 Smith Laboratory on the Columbus campus of The Ohio State University.