The amount of information you can find on your company will depend on what type of company it is. Directories are the easiest way to determine if your company is public, private, international, or nonprofit.
Public - Companies that have stock widely available for trade on stock markets. These companies are required to release financial information - SEC filings, annual reports, etc. - on a regular basis. However, detailed information on internal company practices and policies may be more difficult to find.
Private - Companies whose stocks are not widely traded on stock exchanges. Information on private companies is usually fairly limited and tends to consist of directory-type information and news stories.
International - Companies that are headquartered outside the United States. International companies whose stock is traded on US stock exchanges are required to do annual filings with the SEC. Articles tend to provide the bulk of information available on international companies.
Nonprofit - Company or organization that does not distribute profits to owners or shareholders. Most common types of nonprofits include charities, associations, foundations, etc. Nonprofits file Form 990 annually with the IRS, which are available at Guidestar.org. Otherwise, articles are the primary source of information for nonprofits.