They are passed around on Facebook. From sites like 
http://myfreshnews.com
http://www.angrypatriotmovement.com
http://www.usatwentyfour.com
http://observatorial.com 
http://ilovemyfreedom.org

Sone mix real news with fake, most will make a "quote" headline that shocks when it is about something more boring, but no one reads the actual article it looks like.  Careful going to the sites as they have lots of pop-ups! I read one of the GOP candidate's campaign manager's site to get a taste outside my bubble. He posts these, so I would say it is somewhat mainstream at least.