U.S. Congressional Serial Set (online, 1817-1994)
Contents: Legislative committee reports, memorials, petitions, congressional documents, executive branch documents, annual reports, etc. Bills and resolutions are occasionally found in the Serial Set, especially in committee or conference reports. More sources.
HeinOnline (complete online)
Govt Doc X 25-X 42: (print)
Annals of Congress (1789-1824) (selections online from American Memory)
Register of Debates (1825-1837) (selections online from American Memory)
The Congressional Globe (1833-1873) (selections online from American Memory), Congressional Record (1873-) (selections online from American Memory)
Govt Doc X (print)
Contents: Debate on the floor of the House and Senate. Bills and resolutions are occasionally found in these documents.
Index: Each session has an index, sometimes located in the front, sometimes at the end of the volume. Member's names are better indexed than subjects. Also look for a short history of a bill in the index, or, in the Congressional Record, in a separate section called "History of Bills and Resolutions". More sources.
Statutes at Large (online from American Memory, 1789-1875)
Govt Doc AE 2.111 (print, 1789-present)
Contents: Laws passed by Congress.
Print index in vol. 8 for years 1789-1845; following years have indexes in individual volumes. More sources.