American Demographics Similar content to printed version - if you are looking for demographic info as well as marketing advice, start your search here.

Forrester Research Great information available on web marketing demographics, psychographics and growth.

IDC Research Market information, industry analysis, and strategic and tactical guidance to builders, providers, and users of information technology.

Nielsen Media Research Provides information about competitive advertising expenditures for print, radio and television as well as information about computer usage and the Internet.

Census Bureau  Social, demographic and economic information including current US Population count and economic indicators. 

US Department of Commerce Statistics Access to world-class business, economic, and government information resources on a subscription basis.

FedStats  Access to federal statistics gathered from over 70 government agencies for use by the public.

Bureau of Labor Statistics  Range of current statistics including unemployment rates, consumer price index and productivity indexes. 

FedWorld  Over 150 bulletin board systems and searchable databases operated by the US Government.

Hoover's Directory Searchable database of company profiles, corporate officers, annual reports, market data.

Thomas Register Directory of US companies, brands and products are available.

Corporate Information Good starting point to find company information -  300,000 global company profiles.

KnowX Check the background on a business for less than $10 - find out if a company has any liens against it, if it filed for bankruptcy in the past, and if it has any pending lawsuit.

CyberAtlas US and international research data, targeted to Internet usage and users.

eMarketer Major source for Internet related research, domestic and international.

NUA Loads of surveys about Internet usage. You can get a free newsletter from them telling you when new surveys are out. A good tool.

Internet Sales Discussion Site A good place to get your site evaluated by pros and amateurs. Just reading the commentaries is an education by itself.

WebMarketing Excellent resource with a wealth of articles, research and links.

Digitrends Through its family of information resources, Digitrends inspires interactive marketing strategies through case studies, peer-to-peer exchange, industry news and insightful analysis.

Mediametrix
Provides syndicated audience measurement services, advertising occurrence measurement through its acquisition of AdRelevance, technology measurement and e-commerce measurement services.