I can't seem to find a search function so I don't know if this topic has been done to death, but I recently found a documentary about Esperanto called "The Universal Language."

http://esperantodocumentary.com/en/about-the-film/

At only 30 minutes, it's quite brief and doesn't quite do the subject justice, but it is interesting nevertheless. Also, the filmmaker made another documentary called The Weather Underground, which I think it one of the best documentaries ever made. So he is very skilled at his craft.