These resources are your best bets for finding public company information. Mergent Intellect and Business Insights: Essentials are good places to start for an overview that includes location and contact information, basic financials, and industry codes.
These are your best bets for finding information about private companies.
Strengths, Weaknesses, Opportunities, and Threats! A SWOT analysis is a great resource that gives you a quick overview of a company's strategic situation. Business Insights: Essentials offers SWOTs for public companies. Business Source Ultimate offers SWOTs for public and some private companies.