As re-posted from Portside Labor, which "aims to provide material of interest to people on the left that will help them to interpret the world and to change it."
The National Labor Relations Board webpage describes the rights of employees to act together for their mutual aid and protection, even if they are not in a union.
“Employees shall have the right to self-organization, to form, join, or assist labor organizations, to bargain collectively through representatives of their own choosing, and to engage in other concerted activities for the purpose of collective bargaining or other mutual aid or protection, and shall also have the right to refrain from any or all such activities.” -Sec. 7, NLRA
The page, at www.nlrb.gov/concerted-activity, tells the stories of more than a dozen recent cases involving protected concerted activity, which can be viewed by clicking points on a map.