Basically this [1]
And for who's done it, basically every capitalist nation at this point.
Simply put it's recognizing that capitalism has failings but so does communism. It doesn't seek full state control of everything, just over industries where it's needed. It tries to strike a balance between public and private ownership.
Everything from Vietnam to the US have aspects of market socialism. I think that there are more industries where the US should take ownership, particularly industries that lend themselves to natural monopolies or oligopolies.
Thanks for the reply. I agree that regulating capitalism is necessary, but I also think the "where it's needed" portion of your thesis is a real sticking point.
I would be interested to know what industries you have in mind where the US should take ownership, and in what form.