I stumbled across this site. It’s a kind of guessing game where you try to guess what the original content of a hash value is. Guesses are hashed and then scored by counting how many bits are different from the target hash so a random guess ought to be 512 or so. You’re probably supposed to write a program to do the guessing for you.

Only your lowest score is kept. Can you beat the hash?

Disclaimer: not my site but I’m in love with the idea