Introduction

[Overview]   01   02   03   04   05   06   07   08   09
Processing [processing.org]
  A programming language and environment (based on Java)
  for creating images, animations, and interactions.

The current stable version is 1.5.1 (15 May 2011).

But significant changes are underway for version 2+.
The Pre-Release version is 2.0a4 (05 Nov 2011).

Both are excellent.
(The demos on this website use version 2.0a4)