While the mobile space is huge, it's still not easy to penetrate. Yet, with only $2 million in angel funding over the past couple years, Ringleader has done quite well. The company has put together a sophisticated online advertising network, which helps with mobile ads (as well as those on the desktop). Some of its customers include Best Western, Absolut and Blu-Ray.

Well, now Ringleader has some more juice. That is, the company has raised $6 million from W2 Group, which is a global marketing services company.

"Growth is ramping in mobile ads," said Bob Walczak, the CEO of Ringleader, in an interview with me. He points out that in 2005, the typical ad purchase was a paltry $5,000 to $10,000 per campaign. But, as of last year, it increased to $50,000 to $100,000. "Going into 2008," said Walczak, "we are seeing proposals for seven figures."

There are some big drivers, such as Google (NASDAQ: GOOG)'s Android platform and Apple (NASDAQ: AAPL)'s iPhone. But perhaps the biggest key is that mobile ads tend to get results. "We are seeing click-through rates of 2% to 3%," said Walczak. "This compares to a traditional web ad that gets 0.1%."

Tom Taulli is the author of various books, including The Complete M&A Handbook and The Edgar Online Guide to Decoding Financial Statements. He also operates DealProfiles.com.