Where can I find medical sign language for free?

Though I recommend asking a medical professional that works with the Deaf, a medical interpreter, or a Deaf person for help (and trusting their answers over those from a book), they do have books on medical terms in ASL. If you go to a library (or university library), they may have it. Here is one example:

http://www.amazon.com/Websters-American-Language-M...

I do not know that book, so I cannot vouch for its accuracy or completeness. But books like that do exist, so you may look for something like that.

what do you mean medical sign language? each language has their own sign language, if you mean sign language they use with disabled people then it's called makadon (not sure about the spelling) google should have plenty of links, i remember finding some before.

Deaf MD http://www.deafmd.org/ has a lot of medical terminology in ASL for free. Hope that helps!