State law adds to these, but the federal floor applies almost everywhere.
Minimum wage and overtime. The Fair Labor Standards Act sets a federal minimum wage and time-and-a-half past 40 hours for non-exempt workers. Enforced by the Department of Labor.
Discrimination. Title VII, the ADA and the ADEA prohibit employment discrimination based on race, color, religion, sex (including pregnancy, orientation and gender identity), national origin, disability and age over 40, at employers above small-size thresholds. Enforced by the EEOC, and charges have short deadlines, generally 180 or 300 days.
Harassment. Falls under the same statutes when tied to a protected characteristic and severe or pervasive.
Family and medical leave. The FMLA gives eligible employees at larger employers up to 12 weeks of unpaid, job-protected leave for serious health conditions, a new child, or family care. Your health coverage continues during it.
Safety. OSHA requires a workplace free of recognized serious hazards and protects the right to report unsafe conditions.
Organizing. The National Labor Relations Act protects group action about pay and working conditions, including discussing wages with coworkers, in most private workplaces, union or not.
Retaliation. Every statute above separately forbids punishing an employee for asserting the right. Retaliation claims succeed even where the underlying complaint does not, provided the complaint was made in good faith.
Where to start: wage issues go to the DOL Wage and Hour Division, discrimination and harassment to the EEOC, safety to OSHA. All three take complaints online and none requires a lawyer to file.