Crunchbase

Crunchbase is an online database/social network, mapping the tech ecosystem on the web. It links the companies, personnel, and VCs notable within the industry in a connected way, so you can find out about the people behind a particular venture, their past experience, and their associations with other companies. When searching for competitors, you can use Crunchbase to gain insights into the business, or into the key staff you need to reach or compete with. You can also see information about previous funding rounds.

http://www.crunchbase.com