GlobalEdge Industry Profiles: By Michigan State University, the Industry Profiles page has detailed overviews of 20 industries. Check out the Resources link in the left menu of an industry page for other industry-specific websites. FREE!
Economic Census: A vast source of industry information, including number of establishments within an industry, payroll, revenue, and more. Data can be filtered by geography down to county or city.
Many databases allow for searching by industry codes such as NAICS. NAICS codes, and its older counterpart, SIC, are classification codes for specific industries.
North American Industry Classification System (NAICS)
Standard Industrial Classification (SIC)