Theta Tau is a Professional Engineering Fraternity. It was founded on October 15, 1904 as the "Society of Hammer and Tongs" by Erich J. Schrader, Elwin L. Vinal, William M. Lewis, and Isaac B. Hanks at the University of Minnesota. Being a Greek-letter organization, Theta Tau has lifelong membership and social activities, but the focus is primarily professional.
Theta Tau is the oldest and largest professional fraternity in the field of engineering, with 54 chapters (some inactive) across the United States (as of March 2001). Most chapters are found in the Midwest U.S., but they reach as far as Florida, Arizona, and Washington. The most well-known Theta Tau event is probably the Rube Goldberg competition.
More information can be found at: http://www.thetatau.org/
Note: The "Tau" in Theta Tau is pronounced properly by rhyming it with "saw" or "thaw".