Basic demonstrations of how Processing works, from the Processing.org web site. All of the following demos were written by Casey Reas and Ben Fry unless otherwise stated.
Processing.org Basic Demos
Points and Lines
Vertices (Note: Canvas can't do all styles of curved vertex.)
Triangle Strip (Note: Only normal triangles are drawn.)
Sine and Cosine
Polar to Cartesian
Graphing 2D Equation