quorum - The number of senators that must be present for the Senate to do business. The Constitution requires a majority of senators (51) for a quorum. Often, fewer senators are actually present on the floor, but the Senate presumes that a quorum is present unless the contrary is shown by a roll call vote or quorum call.
Congressional Sessions lists all Congresses and corresponding years - from 1789, when the 1st Congress met, through the current Congress.
You can access legislative information, by bill number or key words, from the THOMAS Web site. Information from the present back to the 93rd Congress (1973) is available on THOMAS.
For information on the Senate, Congress, the legislative process and the federal government, the Virtual Reference Desk is a good place to begin.