TLDR: The coalition is called [StopMegaComcast](http://stopmegacomcast.com/) and includes both public interest groups and rival pay TV providers who are united in their opposition to the merger.
Some of the members include...
* Dish Network * the Parents Television Council * Public Knowledge * the Consumer Federation of America * the Writers Guild of America
[And a few others](http://stopmegacomcast.com/about/)
Huge coalition forms to kill the Comcast-TWC merger for good
bgr.com