RegInfo.gov - Where to Find Federal Regulatory Information
"a United States Government website produced by the Office of Management and Budget (OMB) and the General Services Administration (GSA)."
Regulations.gov - Your Voice in Federal Decision-Making
"is your source for all regulations (or rulemakings) issued by U.S. government agencies. On this site, you can find:
Code of Federal Regulations -- "the codification of the general and permanent rules published in the Federal Register by the executive departments and agencies of the Federal Government. It is divided into 50 titles that represent broad areas subject to Federal regulation."
Federal Register -- "the official daily publication for rules, proposed rules, and notices of Federal agencies and organizations, as well as executive orders and other presidential documents."
The Federal Register: What It Is and How to Use It -- online tutorial
govpulse -- provides visual displays of activity levels for individual agencies (not updated past January 2013)