The U.S. Department of Labor has developed excellent web resources to help employers and employees better understand employment law:

• First Step provides an overview of major employment laws including record keeping, reporting and notice requirements. It also provides details about the information that must be posted within a workplace and downloadable posters to fulfill these requirements.
• E-Law advisors are interactive tools designed to provide easy-to-understand information by simulating an interview with a labor law expert. Pick a topic and the e-law advisor will ask questions and respond based upon your answers.

HRproOnline is a consulting firm specializing in HR issues.  In addition to advertising their services, their website provides a variety of free HR resources including legal information, sample personnel forms and a long list of frequently asked questions.

Idealist.org has created an online volunteer management resource center chock full of articles, guides and best practice suggestions for working with volunteers.

WorkforNonprofits.org maintains a good collection of sample nonprofit HR policies and forms. Although you will likely need to alter the wording to meet your specific needs, these can provide a good starting point when trying to create a sexual harassment policy or put together an exit interview checklist.