Earlier this week, the HeinOnline database announced the completion of its Congressional Record scanning project, which spans 1873-2003 (a scan of the "daily" edition for more current volumes is also available). Hein had already digitized the predecessors to the Congressional Record (the Congressional Globe, the Register of Debates and the Annals of Debates in Congress), meaning that Duke users now have access to a complete, searchable PDF set of the debates in Congress dating back to 1789.
Legislative history researchers at Duke have additional online resources for congressional resources which are too old to be published on GPO Access. The U.S. Congressional Serial Set Digital Collection has been steadily scanning volumes of committee reports, currently dating from 1817-1952 (with an additional 2-3 years being added each month). With GPO Access providing committee reports back to 1994, and the CIS microfiche set in the library covering back to 1970, the digital collection will quickly close the gap in committee report research which has previously been filled by the printed Serial Set available in Perkins/Bostock library.
Committee hearings date back to 1995 on GPO Access, but a digital collection through LexisNexis Congressional provides searchable, well-indexed PDF copies of older hearings, many dating back to the late 1800s.
One frequently-requested but often elusive piece of congressional research is the end result of debates and hearings related to new laws-- the statutes themselves. Session laws are readily available through GPO Access and HeinOnline's U.S. Statutes at Large library, but to locate historical versions of the U.S. Code, researchers usually must look through superseded volumes on Level 1 of the library. GPO Access provides a search of only the 1994, 2000, and (coming soon) the 2006 editions of the U.S. Code. However, there is a glimmer of hope for legislative history researchers: Hein hints in its blog post that the U.S. Code is on its digitizing wish-list...