Mobile ad network InMobi, which recently began building a presence in the United States, just announced that it has raised $8 million in a second round of funding.

The new money comes from Kleiner Perkins Caufield & Byers and Ram Shiram’s Sherpalo Ventures, firms that both invested in the company previously. Anne Frisbie, InMobi’s vice president and managing director of North America, told me the money will help the company pursue its plans for global expansion, both in the US (an effort that began in January) and soon in Japan.

InMobi has built out its network in Asia, Europe, and Africa, and says that it delivers 16.7 billion ad impressions a month. When I interviewed Frisbie last month, she told me the company has been focused on developing its technology, allowing advertisers to target the audiences they want and to automatically improve the targeting as needed.

Frisbee will be speaking today at MobileBeat 2010, VentureBeat’s conference in San Francisco, about how independent ad networks like InMobi can compete as giant tech companies like Apple and Google enter the market.

InMobi has now raised $15 million.