The best solution I know of is simply to google the company name. Study the company's own website pretty carefully. You can pick up quite a bit about a company from what they do and don't put on their site.

Then, you want to check any recent news items you pick up about the company - plus if the company turns up on any of those "disgruntled employee" websites.

I doubt there is one single website where you can find what you're looking for, but a couple hours spent searching the web for company information should give you what you need.
Cheers,
Bev