The magic words to include in your google search for finding online primary source collections are digital collections.
These sites are excellent starting points for discovering the millions of historical resources available online.
Search for archives and collections
Examples of regional cooperative catalogs
Search online resources
Advice from researchers
The more you know about existing government records, the easier time you will have locating them.
You can search indexes of congressional documents online using Congressional Publications (ProQuest Congressional) or FDsys (formerly GPO Access).
An alternate approach is to use the CQ Electronic Library to read summaries and legislative histories written by journalists in publications like Congressional Quarterly (CQ) Weekly. Those summaries can lead you to particular reports and hearing transcripts that can be located either online or in the microfiche Serials Set collection.