Coty points out the release of BF an interpreter for BrainF**k. BrainFk is a small Turing complete langauge with only eight operators. BrainFk fits nicely into the realm of Esoteric Programming. Warning: you can lose a goodly portion of your free time by clicking through that link! I'll plead the fifth and no one will be the wiser.
If however you have some time, I suggest checking out some of the following
INTERCAL is easily the canonical form of esoteric programming. The COME FROM statement is easily my favorite
Malbolge - easily one of the most warped - The author of Malbolge, Ben Olmstead never expected anyone to write a program in Malbolge. Imagine everyone's surprise when Andrew Cooke used a lisp program to grow a hello world program. Cool
BeFunge is a multi-dimensional language in which the IP can move in any of four directions. It also features a unified code/data space to facilitate some interesting hacks
Purists dot org contains an encyclopedia of interesting languages
Turing Tarpit also contains a guide to esoteric languages
Random Programming Languages provides a large list of links