A partial list of universities and colleges that have visited the SIP web site
(some many times)
followed by a list of research and commercial institutions:

Amarillo College, TX
Australian National University
Ball State University, IN
Boise State University, Idaho
Bowling Green State University, Ohio
Brandeis University, MA
Brown Unviversity, RI
Bucknell University, Pennsylvania
California Institute of Technology
California Polytechnic State University
California State University, Fullerton
Carleton College, MN
Carnegie Mellon, PA
Carthage College, Wisconsin
Case Western Reserve University, OH
Catawba Valley Community College, NC
City University of New York, NY
College of William and Mary, VA
Columbia University, NY
Concord College, WV
Cornell Unviversity, NY
Dalhousie University, Nova Scotia
Danish National Library of Science, Denmark
East Carolina University, NC
Florida A&M University
Fort Hays State University, KS
George Mason University, VA
Georgia Institute of Technology
Georgia State University
Gettysburg College, PA
Grant MacEwan College, Canada
Gunma University, Japan
Harvard University, MA
Iowa State University
Kolding Amtsgymnasium og HF-kursus, Denmark
Louisiana State University
Ludwig-Maximilians-Universität München, Germany
Macquarie University, Australia
Massachusetts Institute of Technology
Michigan Technological University
Michigan State University
Moscow State University, Russian Federation
Northern Arizona University
Penn State University
Rutgers University
Seton Hall University, NJ
Shorter College, GA
Simon Fraser University, Canada
Sonoma State University, CA
Southern Baptist University, MO
Southern State Community College, Ohio
Stanford University, CA
State University of New York at Stony Brook
St. Edward's University, TX
St. Gregory’s University, OK
Syracuse University, NY
Texas A&M University
Thomas Jefferson University, PA
Tokyo Gakugei University, Japan
Universidad Tecnologica Nacional, Argentina
Universita' degli Studi di Bari, Italy
Universitat de València, Spain
Universität Karlsruhe (TH), Germany
Universitat Rovira i Virgili, Spain
Universität Stuttgart, Germany
Université Laval, Québec, Canada
Universiteit Leiden, Netherlands
University of Alaska Fairbanks
University of Alberta, Canada
University of Arizona
University of Barcelona, Spain
University of British Columbia, Canada
University of Calgary, Canada
University of California at Berkeley
University of California at Santa Barbara
University of California at Los Angeles
University of Chicago, IL
University of Copenhagen, Denmark
University of Florida
University of Georgia
University of Greenwich, England
University of Groningen, Netherlands
University of Hertfordshire, United Kingdom
University of Illinois at Urbana-Champaign
University of Indiana
University of Innsbruck, Austria
University of Kansas
University of Kyoto, Japan
University of Lisbon, Portugal
University of Louisville, KY
University of Maine
University of Maryland
University of Massachusetts
University of Michigan
University of Minnesota
University of Missouri-Columbia
University of Newcastle, Australia
University of New Hampshire
University of New Mexico
University of North Carolina at Chapel Hill
University of North Carolina at Greensboro
University of North Dakota
University of Osaka, Japan
University of Pennsylvania
University of Pittsburgh, PA
University of Puget Sound, WA
University of Richmond, VA
University of San Francisco, CA
University of Southern Indiana
University of Surrey, England
University of Sydney, Australia
University of Tennessee
University of Texas at Austin
University of Texas at San Antonio
University of the South, Sewanee, TN
University of the Pacific, CA
University of Toronto, Canada
University of Victoria, Canada
University of Wales Swansea, United Kingdom
University of Washington
University of Western Sydney, Australia
University of Wisconsin-Madison
University of Wyoming
Univerzita Pardubice, Czech Republic
Vanderbilt University
Vienna University, Austria
Virginia Commonwealth University
Virginia Military Institute
Virginia Polytechnic Institute and State University, VA
Washington State University
Wellesley College, MA

A partial list of research institutions, observatories, and commercial institutions that have visited the SIP web site:

Apple Computers
Allied Signal
Anglo-Australian Observatory, Australia
American Association for the Advancement of Science
American Astronomical Society
Consejo Superior de Investigaciones Científicas, Spain
Commonwealth Scientific and Industrial Research Organization, Australia
Danish Space Research Institute
Department of Energy
Department of National Defence, Canada
Digital Equipment Corporation
Environmental Protection Agency
European Space Agency, The Netherlands
French National Institute for Research in Computer Science and Control
Goddard Space Flight Center, NASA
ISAS, Japan
Jet Propulsion Laboratory, NASA
Lawrence Berkeley National Laboratory
Lawrence Livermore National Laboratory
Lucent Industries
Lund Observatory, Sweden
Mayo Clinic
Mount Wilson Observatory
National Astronomical Observatory, Japan
National Optical Astronomy Observatories
National Radio Astronomy Observatory
National Oceanographic and Atmospheric Administration
Naval Undersea Warfare Center
Netherlands Foundation for Research in Astronomy
Perth Observatory, Australia
Philippine Astronomical Society
Rockwell International
Sanyo, Japan
Space Telescope Science Institute
Sun Microsystems
Sulzer Technological Corporation, Switzerland
Telespazio, Italy
Observatoire Midi-Pyrénées, France
Office of Naval Research
Osservatorio Astronomico di Bologna, Italy
United States Air Force
United State Geological Survey
United States Naval Observatory
Westinghouse Electric Company