There are trusted wallet cracking services that many people have had success with, Daves is one of them. However as said unless you know at least some of the password and unless it is very short you will have a hard time brute forcing it.
Thanks, dreamspark, for the plug
I agree with the other comments - if you have little or no idea of the password, and it is a decent number of characters in length, then it is effectively unbreakable. If you have a bitcoin wallet encrypted with a 'strong' password, then it doesn't matter whether you throw 1 or 1000 computers or GPUs at it - you will never solve it.
Cheers
Dave
walletrecoveryservices.com