Company Information

General Information:

Hoover’s Online Search for company and industry information.
Corporate Information - Company and Industry Information
CorpTech - look here for information on high tech companies.

Manufacturers/ Suppliers Information:

Thomas Regional - search for industrial suppliers by product/service, company, brand and region of the US. Registration is required but is free.
Thomas Register - national database of manufacturers. Search by name or product/service.
code. Locate Locate a type of business in specific areas

Phone and Addresses:

GTE Superpages - search for companies by categories, business name, city or state.
InfoSpace - search for a company by name or type, city or state. Also available is a reverse lookup - find a name using just a phone or fax number.

Financial:

Edgar Online - Search SEC filings for publicly held companies.

Articles:

Find Articles - search for articles.
BizJournals - search for business journals from major markets nationwide.

Tutorials

How to Find U.S. Company Information
How to Learn about an Industry or Specific Company
Researching Companies Online