supplemental appropriation - Budget authority provided in an appropriations act in addition to regular or continuing appropriations already provided. Supplemental appropriations generally are made to cover emergencies, such as disaster relief, or other needs deemed too urgent to be postponed until the enactment of next year's regular appropriations act.
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.