Google Finance.

Yes (yawn, yawn) another Google product -- Google Finance. As annoying as it might be, the fact is that they keep doing it right. So check it out.

It is in Beta stage at this point (which Google product is NOT in Beta?)

You can search with a company name, stock symbol or even with a general term. I searched for "advertising agency" and it showed 175 results and listed the biggies right there.

I tried Applebee's (my Dad's favorite!) and found:

Market Data
News
Company Facts (revenue, profit, etc.)
Site links: News Releases, Financial Information, Corporate History/Profile, Products/Services, Employment Opportunities
Company Financials Quarterly and Annual Income Statement
Balance Sheet
Competitors
Analyst Estimates
SEC Filings
Major Holders
Discussion Group
Options
Research Reports
Events
Comparison Charts
Company Summary
Management Info
Blog Posts (wow!)

It's well-organized and has real depth. This is a great place to start for getting consolidated information on companies.

Great job, Google. Again.