EDGAR is the Securities & Exchange Commission's (SEC) public website for finding and retrieving required periodic company information filings.
Researchers are often interested in knowing what proportion of a company's stock is held by insiders, large investors, and institutions. Here are some good sources for current information.
The resources found here provide a mix of financial data, company information (including up-to-date news), and industry overviews.
In eStatement Studies you'll find Financial Ratio Benchmark (FRB) figures, broken down by US Region and revenue quartile, for a very large number of industries.
Look here for smaller and specialized industries, like Adhesive Manufacturing or Automobile Driving Schools.