An interpreter for the piet programming language. In this language the programs are pictures, build out of 18 colors and black and white - this is about the real "art of programming".
A programming language in which program flow can go sideways. Closely related to Befunge. Tutorial, reference, sample source code, Public Domain implementation available.
Home of esoteric programming languages such as Java2K, Smith#, Sorted!, [], Esogotschi and the Great Python Language Zoo. Also heavy on the code obfuscation front.