Withholding Calculator
Financial Calculators
U.S. Business Advisor
Billed as the one-stop electronic link to government for business, the U.S. Business Advisor is a collection of links to other government agencies. Topics include doing business with the government, international trade, finance, labor and employment.
Library of Congress
The two most useful areas at this site are Thomas, where you search for information about legislation, and the Copyright Office, where information about copyright law is available.