• Constellation X-ray Mission
• Imagine the Universe

University of California at Berkeley

• Black Holes FAQ

Circinius Galaxy. Hubble. Courtesy of NASA

Cambridge University

• Black Holes: Theory and Evidence

University of Illinois

• Black Holes and Beyond

Harvard-Smithsonian Center for Astrophysics

• Voyage to a Black Hole

Space Telescope Science Institute

• The Truth about Black Holes (lesson plan)