Techcrunch 50 Winner - Yammer

And this year's Techcrunch 50 Winner is... Yammer (think of Twitter for enterprises.)

Yammer takes the familiar Twitter messaging system and applies it to internal corporate communications. There is such a huge demand for this type of service that 10,000 people and 2,000 organizations signed up for the service the first day it launched on Monday. Anyone with a corporate email can sign up and follow other people in their company. But if a company ants to claim its users, and gain administrative control over them, they will have to pay. It’s a brilliant business model.

 If you're interested, go sign up now: Yammer.com