Today is 5/23/2015
From Standard and Poor's. A listing of all the indexes that S&P tracks. Lists of the stocks in each index are generally available.
Detailed research for 8,500 U.S.-listed stocks and an overview for nearly 20,000 non-U.S. stock.
Link to the Fortune 500.
Hoovers is a source of public and private company information with limited free content.