Company information databases provide company status (public/private/subsidiary) and basic directory information. All publicly available information is available - for private companies this may be just whatever has been published in a newspaper or magazine and whatever else the company wants the public to know. Public companies are required to disclose their financials and provide annual reports. Investing professionals provide analysis of mostly public companies and those companies that are planning to become publicly available. The databases listed here all provide basic company information - some have company histories, latest news, SWOT analysis, analyst reports. Company lists based on geography, industry, size, status, growth, etc. are available in others.
Forbes publishes lists of companies such as Best Employers, Most Trustworthy, Global 2000, Most Promising, Most Innovative, Asia's Best, etc.
Fortune annually publishes ranked lists of companies in various categories such as Most Admired, Fastest Growing, Best for Diversity, Best for ethnic groups, etc. Fortune 500 lists the largest, by revenue, American public companies and private companies that file financial documents with a government agency.
Inc 5000 is a list of the 5000 fastest growing private companies in America.