Ning Planning to Remain Free for Teachers - "Ning, a company that allows users to build their own social networks, says it has signed a letter of intent with a major educational publisher to keep its service free for educators, several weeks after causing an outcry among nonprofit groups by announcing that it would end its popular free service. Ning did not give any more information about the deal, which it disclosed as it outlined its plans to begin charging subscription fees to all of its users..." more at http://bits.blogs.nytimes.com
If you have one of the free Ning networks set up and you don't want to upgrade it to a premium site, you might want to look at SaveMyNing. It is a service, self-described as:
"Save My Ning is an archive service that will allow you to backup your existing Ning Network on our webservers for free. We will host ads on the sites in order to cover the cost much like your Ning Network had ads. However, you will not be able to post to your archive, only read it."