Topical 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.
Animation
Sequential
Animated Sprite
Cellular Automata
Wolframs's 1D CA
Conway's Game of Life
Spore 1
Drawing
Continuous Lines
Custom Tool
Pattern
Pulses
Animator
Scribble Plotter
GUI
Rollover
Button
Buttons
Image Button
Handles
Scrollbar
Image Processing
Pixel Array
Histogram
Brightness
Linear Image
Convolution
Blur
Edge Detection
Interaction
Tickle (Firefox 3)
Follow 1
Follow 2
Follow 3
Reach 1
Reach 2
Reach 3
Motion
Linear
Bounce
Bouncy Bubbles
Collision
Circle Collision
Moving On Curves
Brownian
Puff
Reflection 1
Reflection 2
Simulate
Spring
Springs
Chain
Soft Body
Flocking
Simple Particle System
Multiple Particle Systems
Fractals and L-Systems
Koch
Mandelbrot
Tree