Content mills are places that play writers very small amounts for writing articles. I would never suggest that someone looking to make a full time income from freelance writing ever sign up with a content mill.
However, if you want to earn a little money writing when you feel like it and don’t want to go out and find clients on your own then content mills are what you’re looking for. You’re only going to get paid $2-$10 for a 500 word article which is way, way below what you’d get by finding clients yourself.
With those warnings out of the way if you still want to sign up with a content mill here are two that I have tried before: