Now that's something pretty useless...
A simple MD5 brute forcer, written in C.
It calculates all combinations of a given set of characters and compares the MD5 sum of each combination to a given hash. brute calculates about 3 million hashes per second on a Pentium 4 (2,6 GHz). Usage:
brute length hash
length represents the maximal length of a string, i.e. if it's 6, brute won't try words longer than 6 characters. hash is a md5-hash, for example 5cfa779519a9789fad5dfe0de784ee4c