The GAO is the investigative arm of the US Congress, developing reports for Congress on the effectiveness, accountability and efficiency of the government.
Government database of the bills, documents, activities and votes of the U.S. Congress, with full text of legislation from 1993 - present. (Congress.gov replaced THOMAS in September 2014).
HINT: You can also limit Google searches to only display results from .gov (government) websites by adding "site:.gov" (without quotes) at the end of your search. Look at an example search here. Just don't forget to evaluate what you've found!