Can the government shut down your website? What form of censorship does the USA have?

I understand other parts of the world like China and the middle East there is active censorship of the media and the internet itself. The USA is more or less free to put up anything with the exception of child pornography and other materials. What else is censored in the US? What websites can the United States government legally or illegally shut down? If you made a website detailing how to make antrax or something would the government be able to shut down that website? How do people like that wikileaks fool get away with posting all this crazy stuff and not getting shutdown?