Resources for reference:
Humanities:
Voice of the Shuttle
Jefferson Digital Archive
UVa Electronic Text Center
Infomine: Scholarly Internet Resources
Online Books Page UPenn
Social Sciences:
Research and Documentation Online
US Census Bureau
Bureau of Labor Statistics
Edgar: US Securities and Exchange
Additional:
Resources
I have listed some reference resources aimed primarily at college students. These basic reference can serve as the bibliographic foundation for scholarly research.