Obfuscated

BDAMD: Basic Demonic Asinine Multi-Dimensional
Home site, by its creator: descriptions, code samples, download.
http://spots.flatland.com/jms/bdamd.html

Blank
Strange Befunge-descendant language.
http://unefunge.republika.pl/

bogusforth
Obfuscated language, powerful, quite complete, unmaintained, based on forth, "false" (by W. van Oortmerssen), and "TRUE" (by Dewi). By Antonio Maschio.
http://it.geocities.com/tonibin/bf/bf.html

Cat's Eye Technologies
Specifications, implementations, sample source code collections for several strange languages, comments on obfuscated language taxonomy and on several far-out coding practices, mail list, links to many related sites.
http://catseye.tc/projects/eso.html

Comment Programming Language
An open-source language for writing comments.
http://c-p-l.sourceforge.net/

DM's Esoteric Programming Languages
D. Morgan-Mar esoteric languages Chef, Haifu, Ook!, Piet, Whenever. Links.
http://www.dangermouse.net/esoteric/

Esoteric Non-existent Standards Institute
"Institute" for the standardization of unstandardized standardizable things, mostly esoteric languages and extensions to them.
http://esoteric.sange.fi/ENSI/

Esoteric Programming Languages Ring
An organisation started to spread insanity and weird programming paradigms among the masses.
http://homepage.eircom.net/~kmgaughan/esolang/index.html

esoteric.sange.fi
Collection of esoteric programming language implementations, examples, and related files.
http://esoteric.sange.fi/

False
Programming language with two main goals: confusing everyone with an obfuscated syntax, and designing as powerful a language as possible with a tiny implementation: this compiler executable is only 1024 bytes, written in pure 68000 assembler.
http://wouter.fov120.com/false/

l33t
An esoteric language inspired by BF and Beatnik which allows l33t h4xX0r5 to write programs in their native dialect.
http://www.geocities.com/electrodruiduk/l33t.htm

Malbolge: Programming from Hell
Specifically designed to be extremely difficult to program in.
http://en.wikipedia.org/wiki/Malbolge_programming_language

nouse
A language in which the IP (instruction pointer) varies depending on the current stack size.
http://www.geocities.com/qpliu/nouse/

npiet
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".
http://www.gaertner.de/~schoenfr/npiet/

Orthogonal
A programming language in which program flow can go sideways. Closely related to Befunge. Tutorial, reference, sample source code, Public Domain implementation available.
http://www.muppetlabs.com/~breadbox/orth/

Owl
Obfuscated Weird Language: character-based language interpreter written in C, in the style of False. By Antonio Maschio.
http://it.geocities.com/tonibin/owl/owl.html

P-nand-Q
Home of esoteric programming languages such as Java2K, Smith#, Sorted!, [], Esogotschi and the Great Python Language Zoo. Also heavy on the code obfuscation front.
http://www.p-nand-q.com/

Programming in Malbolge
Introduction to Malbolge programming. Also propose modificatins of Malbolge for making programming in it more worse.
http://www.lscheffer.com/malbolge.shtml

Q-BAL Programming Language
A queue based programming language. It's not designed to be useful, just fun.
http://homepage.tinet.ie/~kmgaughan/esolang/q-bal/

Shakespeare
A language with beautiful source code that resembled Shakespeare plays.
http://shakespearelang.sourceforge.net/

Turing Tarpit
Directory of sites dealing with obfuscated programming languages.
http://www.geocities.com/ResearchTriangle/Station/2266/tarpit/tarpit.html

The Unlambda Programming Language
Minimalistic functional language based on the Lambda calculus but lacking the Lambda operator. Tutorial, reference, GPLed interpreters available.
http://www.madore.org/~david/programs/unlambda/

Waduzitdo
Turing incomplete programming language written by a guy named Larry, who's friends always asked him about his new PC: "What does it do?" Works via 2 registers: accumulator and match flag which holds one value (T or F).
http://www.geocities.com/ResearchTriangle/Station/2266/tarpit/waduzitdo/

Weird Programming Languages
Yet another list of obfuscated programming languages.
http://members.tripod.com/rkusnery/weird.html

Whitespace
Any non whitespace characters are ignored; only spaces, tabs and newlines are considered syntax.
http://compsoc.dur.ac.uk/whitespace/

XS: XML-based Obfuscated Programming Language
Toy language. Harness the power of XML, by using it as a programming language. Compiler, sample code; interesting speculations on language design. By Mark Carter.
http://www.markcarter.me.uk/computing/xs.html

ZT
The esoteric programming language. Documentation, interpreter, and example programs.
http://www.philipp-winterberg.de/software/zte.htm