AMSAT
- http://www.amsat.org/
- Information regarding amateur radio satellite communications. Also available are Keplerian elements in several formats, updated weekly.
CelesTrak
- http://www.celestrak.com/
- Keplerian elements for most satellites in low-earth orbit. Also includes historical archives dating back to 1980 and information about satellite tracking.
Project Oscar
- http://www.projectoscar.net
- International amateur satellite organization - web site contains info about amateur satellites, operating information, status of individual satellites and an online tracking application.
Safety Track
- http://www.safetytrack.net/
- Global Positioning System for law enforcement, private and commercial users to track vehicles. Complete information, plus a demo.
SatScape
- http://www.satscape.co.uk
- Windows tracking software; features include 3D maps and can track several hundred satellites simultaneously.