Wikipedia
Heavens-Above
Heavens-Above is a non-profit website developed and maintained by Chris Peat as Heavens-Above GmbH. The web site is dedicated to helping people observe and track satellites orbiting the Earth without the need for optical equipment such as binoculars or telescopes. It provides detailed star charts showing the trajectory of the satellites against the background of the stars as seen during a pass. Special attention is paid to the ISS, Iridium flares, and space shuttle missions. The website also offers information on currently visible comets, asteroids, planet details, and other miscellaneous information.
Sky & Telescope magazine described Heavens-Above as "the most popular website for tracking satellites."