New York Times
University of Washington physicists determining the value of the gravitational constant.
S. Smullin et. al., Stanford University - This research group is measuring the force of gravity on very-small-length scales and testing Newton's and Einstein's models of gravitation.
Google - Research database allows searching of the scholarly literature.
T. Henderson, The Physics Classroom - An excellent tutorial on Newton's theory of gravity, including practice exercises.
J. Imamura, U. Oregon - A summary of Newton's laws, their shortcomings and Einstein's theories of gravity.
R. Nave, Hyperphysics - A detailed look at inverse square relationships throughout physics.
An alphabetical glossary of relevant scientific terms.
I. Newton - A reproduction of the preface to Newton's famed Principia (1687) and links to the full text.
A photograph of Newton's own copy of the Principia and the fabled apple tree.
B. Willis, Worsley School - A simulation of the effect of gravity on orbiting bodies. Illustrates Kepler's laws on which Newton based his theories.
U. Kruse & T. Tran, U. Saskatchewan - A detailed explanation of the Cavendish Experiment, including a simulation.
M. Fowler - Java simulation of projectile motion as Newton envisioned it.