groupon logoGroupon, a service that uses “collective buying power” to offer shopping deals, has added more funding in a big way with a new $30 million round led by Accel Partners.

Here’s how it works: Groupon offers a single big deal of the day like half-off wine tasting for two in Napa. But they only happen if enough users sign up.  You don’t have to know the others. But if there’s a deal that you’re particularly excited about, you have an incentive to tell your friends.

Chicago-based Groupon offers deals for 26 U.S. cities. (VentureBeat writer Kim-Mai Cutler recently wrote about this collective shopping concept, describing a similar service from LivingSocial.)

This shopping service is an outgrowth of The Point, a site that tried to coordinate this kind of collective action, but for social change, not bargains. The company previously raised $4.7 million from $4.7 million from Rugger Ventures, Old Willow Partners, and New Enterprise Associates.

Groupon launched in November 2008 and says users have signed up for 800,000 deals totaling $36 million in savings.