From the CSETI website:

The Center for the Study of Extraterrestrial Intelligence (CSETI) is an international scientific research and education organization dedicated to the furtherance of our understanding of extraterrestrial intelligence. CSETI was founded in 1990 by Dr. Steven M. Greer, who is the International Director. CSETI's projects include the CE-5 Initiative, and the Disclosure Project.

CSETI is especially interested in the ETI-Human relationship and in the peaceful furtherance of this relationship. A thorough review of existing data and documents concerning "UFO's" indicates that the Earth has been visited by ETI and Extraterrestrial Spacecraft (ETS) for decades, if not centuries, and that this contact has intensified since 1947.

There is a great deal of compelling evidence for the ongoing contact between ETI and humans. This evidence includes the existence and authentication of top secret documents confirming the retrieval of crashed ETs and their occupants, the numerous photographs and films showing ETS, the reports of thousands of credible civilian and military observers, and the presence of associated landings.

CSETI is committed to the thoughtful long-term development of bilateral ETI-Human communication and exchange, and open public education on the subject. We regard this endeavor as the most important scientific and educational project of the next thousand years and invite you to join us.

CSETI is supported through the voluntary efforts of its friends around the world. Please network people to our websites so they may see the wealth of evidence for themselves.

(Not to be confused with Gilliland's ECETI).

Note that the current status of CSETI is unclear: it was absorbed by the Sirius Disclosure Project and became one of its sub-projects, but its new 2018 website seems to indicate it is an independent project again.