These examples are running online through Processing.js using HTML5 Canvas and WebGL for rendering. There are many more examples included with the Processing application; please look there if you don't find what you're looking for here.
Structure
Statements and Comments
Coordinates
Width and Height
Setup and Draw
No Loop
Loop
Redraw
Functions
Recursion
CreateGraphics
Form
Points and Lines
Shape Primitives
Pie Chart
Triangle Strip
Bezier
Bezier Ellipse
3D Primitives
Data
Variables
Integers and Floats
True/False
Characters and Strings
Datatype Conversion
Variable Scope
Arrays
Array
Array 2D
Array Objects
Control
Iteration
Embedded Iteration
Conditionals 1
Conditionals 2
Logical Operators
Image
Load and Display Image
Background Image
Transparency
Alphamask
CreateImage
Pointillism
Shape
Load and Display Shape
Disable Style
Scale Shape
Get Child
Color
Hue
Saturation
Brightness
Color Variables
Relativity
Linear Gradient
Radial Gradient
Wave Gradient
Math
Increment/Decrement
Operator Precedence
Distance 1D
Distance 2D
Sine
Sine and Cosine
Sine Wave
Additive Wave
Polar to Cartesian
Arctangent
Graphing 2D Equation
Random
Double Random
Noise 1D
NoiseWave
Input
Mouse 1D
Mouse 2D
MousePress
Mouse Signals
Easing
Constrain
Storing Input
Mouse Functions
Keyboard
Keyboard Functions
Milliseconds
Clock
Transform
Translate
Scale
Rotate
RotateXY
RotatePushPop
Arm
Objects
Objects
Multiple Constructors
Composite Objects
Inheritance
Lights
On/Off
Directional
Spot
Reflection
Mixture
Mixture Grid
Camera
Perspective
Move Eye