The Health Insurance Privacy and Accountability Act included legislation focusing on administrative simplification.

The standards for the various transaction sets can be viewed and downloaded here:

Transactions and Code Set Standards

The various identifiers contained within the transaction sets can be accessed here:

Identifier Standards

The official privacy rule was finalized on August 14, 2002.  It can be downloaded here:

The Privacy Rule

Additionally, there is a specific rul passed regarding security of information:

The Security Rule