-By Mike Shields

Internet radio upstart Pandora has streamed 3.3 million songs to iPhone users since the launch of its new mobile application, making it the third most popular such application for the red hot device—the newest version of which Apple released on July 11.

Pandora’s success on the new iPhone, which sold a stunning one million units this past weekend, could thrust Internet radio to new heights, as the until now still-under-the-radar medium appears ideally suited for mobile usage. Pandora, which boasts of a proprietary technology designed to help users discover new music that matches their specific personal tastes, says it’s been setting listening records since its iPhone app went live.

As of July14, the company had registered 180,000 new users, and more than 200,000 new stations had been created on the iPhone. Pandora executives claim that the company has attracted a new iPhone listener every two seconds since the launch, with most listeners spending close to an hour per day listening.

This level of intense engagement is likely to excite the ad community, which has been patiently waiting for more mass buying options in mobile media. Pandora, which has been restrained in its approach to advertising to date, is promising to roll out a new mobile marketing platform later this year.