While searching for employment law resources with a nonprofit perspective, I discovered the site of the Pro Bono Partnership, a leading provider of free business legal services, educational workshops and other legal resources to nonprofits in Connecticut, New York, and New Jersey. The site includes what appears to be a fairly comprehensive "Employment Law Guide for Non-Profit Organizations" which acknowledges a number of highly reputable big law firms for their contributions. I must warn you that much of employment law is state-specific, but even if you’re not in the states addressed by the Guide, you may find some valuable information within on issues such as interviews, privacy issues, the employee-independent contractor distinction, federal wage and hour laws, harassment, discrimination, and ending the employment relationship.
You can access the Employment Law Guide for Non-Profit Organizations here.