Yammer, which creates something akin to an internal Twitter for businesses, is raising big money:

In the four years since its inception, Yammer has been implemented by over 85% of the Fortune 500. In 2011 alone, the company tripled sales, employees and licensing. This momentum allowed the company to raise US$ 85 million in its fifth round of funding, which was led by venture capital firm Draper Fisher Jurvetson, for a total of US$ 142 million in financing.

Yammer is one of the few things I miss regularly about my former job.