Code of Federal Regulations
Rules made by federal agencies and executive departments. 

Constitution, Statutes, Legislative Bills, Legislative Resolutions
List of titles, popular names, sections, full text search for the US Code from LII.

Constitutions, Statutes and Codes
US Constitutions, Statutes and Codes at Federal and State levels from Cornell Law School, Legal Information Institute (LII).

Federal Register
The official daily publication for rules, proposed rules, and notices of Federal agencies and organisations.  It also contains executive orders and other presidential documents.  Published by the Office of the Federal Register, National Archives and Records Administration.

Michie
A member of the LexisNexis Group, Michie provides selected statutes, codes and rules for California, Delaware, Maryland, Mississippi, New Mexico, South Dakota, Tennessee, Utah and Vermont.