This site from The Galileo Project of the Rice University provides a great look into the pendulum experimens of Galileo. Contains first-hand writings and examples of experiments along with links to additional information.

The history of the pendulum and its importance both in timekeeping, and in how timekeeping was used to solve other problems, such as determining longitude on a map.

Article outlining the scientific history behind the evolution of theories about measuring time based on the movement of a pendulum, and about how gravity would impact a pendulum's movement depending on one's proximity to the Earth's...