Family Educational Rights and Privacy Act (FERPA)
Official summary of FERPA
Welcome to AACRAO's Online FERPA Guide
FERPA guide for higher ed, with more detailed explanations of what constitutes directory information vs. personally identifiable information. According to this, email addresses are OK to disclose, which isn't what I was previously told.
FERPAPoint2005.pdf (application/pdf Object)
FERPA guidelines for online education, include what laws apply and what don't