256-bit encryption is still nowadays secure. In computer theory it's quantum computers that some decades later may revolutionize decryption, but modern supercomputers can't do it.

If interested you can try something like:
http://www.golubev.com/hashgpu.htm
It even uses GPU power to greatly utilize all the power computer has for MD5 hash cracking. If you assume that word is only 1..8 characters long (256-bit would mean 32 characters) and only contain small letters from a..z it will take many hours. Now add numbers and big letters in the force and it'll take forever...