Unlawful termination of employment: Any Suggestions, Web Sites, Resources..?

I recently was terminated from my job as a hotel night auditor.. The reason for said termination, Is because my employers believe that i stole 66$ from our sales drawer.

I've told them 1000 times that i didn't take anything, but i cannot understand where the money exhists or why its being asked for. There is much more too it, and i'll save you the details..

The bottom line is that I DID NOT TAKE the money.. I have done many unlawful things in my past, and i'm not afraid to fess up to any of them... But this time I'm completely innocent.. I'm being punished for something i did not do.. I'm figuring that with enough investigation this fact could be brought to light..
I'm now terminated and cannot get access to said paperwork... How can i lead an investigation into this issus..

I live in the State of Massachusetts... and the company is True North Hotels DBA marriott..