I first read about the Processing language many years ago. It was introduced as a "Flash Killer". In the end, other factors killed Flash - but certainly not Processing... It is the language of choice for programming the DIY Arduino board, and that has given it exposure to a moderate audience.

In its 2.0 beta implementation, Processing has been ported from Java Applets to JavaScript, making it more accessible for browser-based delivery. Either way, it's great for generative art and visualization projects (especially following the demise of Flash).

Lines Circles - Move the circles by moving the mouse. Simple..
Lines Clock - Got time?.
Lines Lines - Draw random lines to the edge of the screen, or until we hit another line.
Cosmos Cosmos2 - Based on the LIFE algorithm, except rather than viewing this as a Petri Dish of tiny life forms, I see it as the Cosmos - vast and distant, but also in a state of constant change.
Waves Waves - Patterns using sin waves and triangle strips.