AdMob’s January report shows Apple’s iPod Touch with the highest rate of growth among mobile devices capable of browsing the Internet.

The number of worldwide requests from the iPod Touch rose from 4.7 percent in December to 7.4 percent in January, by far the biggest increase of any mobile device. The iPhone’s share rose from 10.8 percent to 11 percent.

Last month an AdMob report on ad requests from mobile devices showed the iPod Touch second only to the iPhone. AdMob supplies online ads to such devices, most of which are cell phones.

Like the monthly reports on Web usage from Net Applications, the AdMob data is not scientific, but can illustrate trends over time.

For what it’s worth, the January report from Net Applications jibes well with the data from AdMob. It’s clear more and more people are using the Internet capabilities of their iPhones and iPod Touches.

As was the case in January, the iPhone and iPod Touch are No. 1 and No. 2 in AdMob’s latest report, with Motorola’s RAZR V3 a distant third and slipping further behind – it lost 0.4 percent.

The Nokia 6300 was the only other device other than the iPhone to register even a modest 0.2 percent increase.

Apple also gained ground on Nokia in the AdMob data broken down by manufacturer. Nokia’s share increased from 29 percent to 30.1 percent, but Apple’s increased from 15.5 percent to 18.3 percent. Third-place Motorola’s share slipped 1.8 points to 9.9 percent.

In the U.S.-specific data, Apple’s mobile platform did even better. Among the handsets, the No. 1 iPhone picked up 0.7 points, generating 16.8 percent of January’s ad requests. But the iPod Touch gained a stunning 5.2 points, reaching 12.3 percent.

The iPhone/iPod Touch’s combined total of 29.1 percent opened up Apple’s lead in the list of manufacturers in the U.S. data. Apple’s 5.9-point gain coupled with Motorola’s loss of 2.3 points and Samsung’s loss of 1.3 points shows how rapidly the momentum is shifting towards Apple’s nascent mobile platform.

AdMob data from Western Europe shows similar Apple dominance. There the iPhone leads among devices with 21 percent of requests, followed by the iPod Touch with 10 percent.

In the operating system data Apple has an even larger lead, an anomaly that holds true in several geographic categories. The iPhone OS made 44 percent of all worldwide ad requests, 51 percent of those from the U.S. and 52 percent of those from Western Europe.

With Apple staking out a big chunk of territory in the mobile Web space, its competitors – primarily RIM, Nokia and Palm – still need to prove they can keep up by building devices people will want to use not just to make calls, but to access the Web.