If it has a relevant / short / se friendly domain name, you can try to sell the domain name by itself. There are not that many people out there that want to deal with movie streaming sites. Too much liability.
You can try websitebroker.com and flippa.com but as was mentioned you will have some difficulty without a licence to distribute the material you are streaming.
You're probably going to have a hard time selling a movie streaming website for many reasons. One of the key reasons would be if you aren't licensed to stream the movies and are doing it illegally. Another being that movie streaming websites come and go for one reason or another so you would have to have a good reason why people would want to buy yours when they can just buy a domain and create their own cheap. Depending on what the domain name is, it might be better and/or easier to just sell the domain name if it's of any value.
Like any other site, you can sell in on Flippa or I would suggest to go to blackhatforums. There you will find serious buyers.