I used to stream from Netflix all the time when I had the service. It's a great way to get caught up on old shows you've missed, as well as some nice movies. I don't have Netflix right now, but have watched a few movies on YouTube, and I will stream about one a month on Amazon. They used to have a specific category for Special Deals, but I don't see it anymore. I loved perusing that section and being able to stream a couple a month.
Whether or not its illegal - I think perhaps depends on what country you live in - as providing your doing it purely for personal use and not for monetary gain - its not illegal to download or stream TV programs and movies where I live - in fact its something that I do all the time - for the simple reason - that as there is no TV signal here - its the only way that I get to watch TV. However although it used to be a bit fiddly - as I used to have to download all my favorite programs and movies onto a flash drive and then plug it into the Blu-ray so that I could watch them on the TV - since investing in a Media Player at the end of last year - its now way easier - as all I have to do is plug the player into the TV and I can watch movies and TV programs either downloaded or streamed directly via the internet for free and in high definition too.
I was surprised to discover all of the movies available on YouTube. I had looked there before for one particular television show that I kept missing due to police chases, and noticed there were movies, but back then, a lot of them lagged, were dubbed, or had very poor quality, so I ruled it out as a source of entertainment. Recently, I was looking for a movie clip on there, and stumbled upon quite a few full length good movies, so I'll be looking there in the future, as well.