Ranking a company's influence in the iPhone universe is no easy science. That's why FastCompany.com has partnered with YouNoodle in an effort to mine the 25 companies that are fast becoming the power players of Apple's mobile world.

The rankings below aren't meant to tell you which apps are most useful or appealing--that's another story. The companies here are ranked by an algorithm that digests a different kind of data: it measures the traction of iPhone companies, the money they're making and their brand buzz.

The criteria are varied. Some are bottom-line: how many app downloads? How much revenue? How much venture funding? Others try to measure a different kind of relationship: how many iPhone developers have built on a company's API? How many times is this company mentioned alongside the iPhone in the press?

Think of this list as a way to understand who will get to shape the personality of the iPhone as it grows. It also explores all the different currencies that have grown up around the platform; the App Store isn't just about dollars and cents, but also branding, advertising, engineering and design. Apple's popularity lists only scratch the surface.

Of course, there will be contention. Right now, we've limited the list to private companies, and we haven't differentiated between developers like Smule and Ngmoco, and platforms like Twitter and Facebook. As we update this list, we'll add more ways to slice the rankings and more data to mash up. We'll also be evaluating how we weigh the criteria above. As always, we welcome your comments and your suggestions.