The growing popularity of the iPod touch — Apple’s AAPL iPhone without the phone — finally registered in the Internet market share data gathered every month by Net Applications.

Stuck for three months running with a 0.11% share of Web traffic, the iPod touch’s share in April jumped to 0.15% — a 36% increase in one month, according to preliminary data released overnight Friday. See the chart below:

The iPhone also gained share, up 12% to 0.55%, and Linux rose 13% to grab a larger than 1% share for the first time. But neither could match the iPod touch’s growth rate.

Microsoft’s MSFT Windows and Apple’s Mac OS X were each down a hair, to 87.9% and 9.73%, respectively.

Apple doesn’t break out iPod touch sales in its quarterly reports, but COO Tim Cook characterized it as a “runaway hit” during the company’s second quarter earnings call last week and reported that sales had doubled year over year.

He also released enough information for analysts to calculate that Apple has sold at least 15.83 million units (37 million – 21.17 iPhones) since the iPod touch was launched on Sept. 5, 2007.

To see Net Application’s May 1 report, click here. The month-to-month comparisons are summarized in the table below.

Net Applications’ monthly surveys are conducted by sampling browser data from some 160 million visits to websites operated by the firm’s clients. The Web metrics firm describes the results as “market shares,” but they do not actually measure share of market in the traditional sense of revenue or unit sales. They do, however, provide a consistent methodology by which to gauge operating system trends. (See Ars Technica for a good review of the different ways to measure market share.)