Understanding orbits can be called the key to understanding satellites. These videos by Nanosatisfi cover many facts about orbits.

Watch Coding For Space – Orbits 1

This second video about orbits covers the math involved in calculating a pure circular orbit.

Watch Coding For Space – Orbits 2

Physics Classroom: Mathematics of Satellite Motion http://www.physicsclassroom.com/class/circles/u6l4c.cfm

PLAN-13 Satellite Position Calculation Program by James Miller G3RUH
http://www.amsat.org/amsat/articles/g3ruh/111.html

Nanosatisfi http://www.nanosatisfi.com/