The Congressional Research Service, an arm of the Library of Congress, serves the legislative process by providing Congress with non-partisan and in-depth legislative research and analysis on a variety of topics. CRS produces or updates more than 3,000 studies and other publications each year, none of which are distributed to the public. However many sites host reports relating to their main mission/interest providing a great public service.
Codified (organized by topic) version of all federal laws currently in force. Various sites offer the U.S. Code online, each with slightly different search features and tools. Classification guides show where newly passed legislation will be entered into code. Popular names tables translate the popular name of law to the official title.