C-SPAN now offers a digital archive of Congressional proceedings all the way back to 1987. So if you are performing legislative history, want to see debate from a popular Bill, or would like to view testimony from a hearing, this is a great resource. Every C-SPAN program aired since 1987, almost totaling over 191,000 hours, is contained in the C-SPAN Archives and immediately accessible through the database and electronic archival systems developed and maintained by the C-SPAN Archives. The programs are indexed by subject, speaker names, titles, affiliations, sponsors, committees, categories, formats, policy groups, keywords, and location. The congressional sessions and committee hearings are indexed by person with full-text and all videos can be searched by users.
Here is a link to the website.