The NLRB has launched a page which describes cases of protected concerted activity.  The page states that employees have the right to act together to improve their pay and working conditions even if they are not part of a union.  

The page tells the stories of more than a dozen individuals and groups who have been involved in protected concerted activity. The site includes a map which demonstrates the areas where the activity took place.  Viewers can click on the markers and the story of the activity comes up.  The narratives include the story of the housekeeping employees who protested a wage cut, the story of employees at a plastics manufacturing plant who were disciplined for complaining about a supervisor who turned out to be a registered sex offender, and the story of employees of a major homebuilder who were misclassified as supervisors, so that they would not be paid overtime pay.  

The page provides information defining protected concerted activity and lists a number for the National Labor Relations Board which people can call for answers to questions about concerted activity.  The site can be found at http://nlrb.gov/concerted-activity.