Canvas Coordinates
This page uses mouse tracking within an HTML5 canvas element to display polar and the equivalent Cartesian coordinates. It's a sort of educational tool for showing how the two systems work and how they relate to each other.
Whilst mouse tracking was possible prior to the arrival of HTML5 it's much easier now. It's a good tool if you have graphs or charts on your website and is useful if you have an idea for a web based game.
