The short answer is yes. The National Labor Relations Act (NLRA) protects the right of employees to engage in protected, concerted activity. Protected activity includes action related to terms and conditions of employment, including salary, benefits, hours, and other working conditions. Concerted means at least two employees are involved, and can include one employee acting on behalf of others.
Say your employer gives you a raise, but asks you to keep it quiet from the rest of the staff. Your employer has committed an unfair labor practice. Prohibiting employees from talking about salary is a violation of Section 7 of the NLRA, which gives employees the right to talk to each other about terms and conditions of employment. The NLRA applies to union and non-union employees alike.
If you believe your employer has violated your rights under the NLRA, you can file a charge with the National Labor Relations Board (NLRB). They will perform an investigation to determine if a violation occurred. The NLRB has the power to issue temporary injunctions and enforce remedies such as backpay and reinstatement. Visit their website for more information (www.nlrb.gov). Of course, it is a good idea to seek the help of an attorney to help you navigate the legal aspects of your complaint.