Federal Government Resources

Internal Revenue Service

Site allows business owners to apply for employer identification numbers and file and pay federal taxes.  Also, many resources are located on the site regarding federal tax regulations for businesses.

FirstGov.gov

The US government's official web portal.  It features online services for businesses such as filing patents and trademarks, government sales and auctions, and other resources available from the federal government. 
 
United States Census Bureau, NAICS Division

This site contains information about the North American Industrial Classification System (NAICS) as provided by the United States Census Bureau.