Yammer, the Twitter for business users, has raised $5 million in its first round of funding from Charles River Ventures and the Founders Fund, the $200 million fun started by ex-PayPal employees. Incidentally, Yammer CEO David Sacks worked at PayPal as its COO. Unlike Twitter, Yammer has been focused on earning revenues from its launch early last fall. Members can sign up and use the service for free, but once a company joins officially—which gives it a few more features such as more security controls—it pays $1 a month for each employee using it.

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Yammer has gotten some good feedback, where it has infiltrated large firms including the BBC and Telefonica. But it’s not the only service in the space; Present.ly and WizeHive, also pitching themselves as the enterprise version of Twitter, have recently sprung up. As for the actual Twitter itself, TechCrunch notes that the service could easily pitch itself to business users simply by offering them a groups feature, as they already do in Japan.