The Library of Congress just recently launched Congress.gov as a new online repository for U.S. legislative information. Although the site is still in beta testing mode, you can currently search across the following content using a new search engine LOC boasts has a "user-friendly design":
"legislation from the 107th Congress (2001) to the present, member profiles from the 93rd Congress (1973) to the present, and some member profiles from the 80th through the 92nd Congresses (1947 to 1972)."
According to a Library of Congress blog, Congress.gov will eventually replace Thomas.gov next year. As you may know, Thomas,gov has historically been the 'go-to' place for federal legislative history and information. Among other data and information you will still need to use Thomas.gov for include legislative searching back to the 101st Congress (1989), contains House and Senate roll call votes, the Congressional Record since the 101st Congress (1989), Committee information, Presidential Nominations back to the 100th Congress (1987), and Treaties since at least the 94th Congress.