Wolfram Research
Wolfram Math World: Midpoint
This MathWorld site offers a lesson on finding the midpoint of a line segment using a compass and finding the midpoint of the sides of a triangle. This site also has an interesting way of drawing two triangle with equal area by finding...
Varsity Tutors
Varsity Tutors: Hotmath: Algebra Review: Midpoint Formula
Find a quick, concise explanation of the midpoint formula. An example is given and clearly explained for the midpoint formula in one, two, and three dimensions.