Brain***** (or BF, for short) is a Turing tarpit , designed to challenge and amuse programmers The language consist only on eight commands, yet is Turing complete.
This interpreter features:
INSTALL file included in the source tarball
for compilation and installation instructions, and the
ChangeLog for a summary of changes between versions
A place where you can find a lot of BF programs for testing this and other interpreters is The BF archive, in the directory bf-source/prog. Apart from the proverbial hello_world.b program, other interesting examples are prime.bf, wich calculates prime numbers, or a Fibonacci numbers generator.
As a much larger and complex example you can try Lost Kingdom, an adventure-like game written in bf.