Here are some links you should find helpful:
The Congressional Budget Office publishes many useful reports relating to Federal taxes and spending, as well as the economic effects of various laws.
The Government Accountability Office studies the efficiency and effects of Federal spending programs.
The Library of Congress Congress.gov page (formerly “Thomas”) allows you to read the Congressional record, find the text of bills, and look up information on individual members of Congress.
The Federal Register, published daily, includes presidential Executive Orders, proclamations, etc., as well as proposed and final regulations.
A Century of Lawmaking for a New Nation, another product of the Library of Congress, allows you to reach and electronically search the text of the Constitutional Convention, the Continental Congress, and newspaper accounts of Congressional activity until 1873. It also includes the Congressional Record from 1873-1875, as well as many other 18th and 19th century government documents.