The new ad types reflect innovations requested by advertisers since AdMob first introduced ad units tailored to the iPhone a year ago, according to Jason Spero, the company's vice president and general manager for North America. "They're almost all advertiser-driven," said Spero, whose company reached 13.4 million unique iPhone and iPod touch users worldwide in April.

With mobile social networking rapidly growing, it's not surprising that marketers would be keen to take greater advantage of the trend. To that end, AdMob will offer a unit that provides links to brand pages on social networks such as Facebook, MySpace and Twitter after someone clicks through to help deepen consumer engagement through a campaign. "This extends the dialog with the user, if you will," said Spero.

AdMob is also combining search and display in a separate new format that will allow advertisers to add search boxes to banner ads so users can type queries directly within the units. The ads would enable people would be able to search a brand's mobile site or other database, such as an automaker's inventory of used car models at local dealerships. "E-commerce folks are very interested in this," noted Spero.

But he added that search engines could also use the units to promote their services. Google is the default search provider on the iPhone -- but Microsoft, for instance, could use it to push its new Bing search offering.

The other two new ad formats expand options for rich media placements on the iPhone. One -- a multi-panel unit -- provides interactivity and animation with multiple calls to action in a single rich media unit. The other, a "scrolling canvas" unit, expands to a full mobile Web page when tapped without requiring users to click away from a site or iPhone application.

The search and social ad units will be available for both the iPhone's Safari browser and within iPhone applications, while the rich media units will only be available in apps. The social networking and rich media ads will be priced on a CPM basis, while the search ad will be sold on a CPM or cost-per-search basis. But Spero added that the pricing models for the new units are still evolving.

To help ensure that app developers can accommodate the new ads when they launch, AdMob is releasing the new version of its software development kit on Friday. "Free apps rely on advertising, so developers are constantly looking for ways to maximize monetization," said Spero, who noted that AdMob serves ads on more than 1,500 apps. With the iPhone 3.0 OS giving developers the ability to ad e-commerce elements to apps, they will have another way to derive revenue from their creations.

While the ads that AdMob serves on the iPhone are roughly evenly split between the mobile Web and apps, Spero said advertisers are mainly interested in reaching certain audiences regardless of the platform. "The majority of advertisers come to us and say, 'how many females 18 to 34 can you give us, or some other demographic," he said.

AdMob overall says it serves 6.2 billion mobile banner and text ads monthly across a wide variety of mobile sites, apps and devices that also include the BlackBerry, Google Android-powered phones and Symbian-based phones.