Twitter may have amassed a sizable following, but six weeks after its launch, microblogging service Yammer—or Twitter with a business model as its being called—is already bringing in revenue, albeit small. The service, based in West Hollywood, California, is aimed at the corporate crowd and and as CEO David Sacks told the NYtimes.com, tries to help workers be more productive. Instead of asking, “What are you doing?” as Twitter does, it asks, “What are you working on?” The idea is apparently to stop all those emails that can be quickly answered from blocking up email boxes.

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So how does it earn money? Anyone with a work email can sign up for free. But if a company wants to join officially—which gives it more control over security and how workers use it—they must pay $1 a month for each employee signed on. The startup currently has 10,000 companies with 60,000 users signed up. Of those, 200 companies with 4,000 users are paying for the service. Some of the companies, too, are quite impressive. Telefonica (NYSE: TEF), the Spanish global operator, uses it in its 350 member R&D unit, while the UK’s BBC has some 500 employees trying it out. Twitter, meanwhile, is still casting about for a business model.