Key Websites for Processing
http://processing.org/
http://www.learningprocessing.com/
http://www.openprocessing.org/
Some Examples and Inspiration:
Below is piece created using processing and shape outines. The outlines of the shapes move and create 3D patterns with lots of texture and bright colours using differnt opacities. This piece could be developed into a great interactive piece that changes colour when the mouse is clicked or moves with the mouse.
Below is a non interactive tree that grows and from one stem and flowers. The part that really makes this for me is the fact that you can see the previously drawn trees slightly faded belind. This gives the image alot of depth.
This is an interactive piece that follows the direction of your mouse. If you click it resets the image. I think this is a basic looking interactive piece but iw works well with grey scale to show depth to the image. Could edit by adding different colours.
This is another interactive piece that i really like. You can make the hair move by passing the mouse overtop of the image or make it bounce by clicking on the image. I think this is a really fun little interaction.