Below are some good websites to investigate a company's background information.
comprehensive career search on the company and the industry.
SEC filings information. Every incorporated company must register with this.
3) Department of corporation/business in every state government
It has a searchable database of companies. Job seekers can look up a company by name or search by industry, city, state, country, and number of employers and revenue to generate a list of potential employers. There may even be message boards where you can get the inside scoop on the company culture and on what's happening.
5) Local chambers of commerce, local business newspapers, and the business section of your local newspaper.