Apple, Facebook, and Twitter are among the bleeding-edge tech players generating buzz -- and a buck -- by enlisting the aid of legions of independent software developers.

The idea is catching on. Now companies from such industries as retail and media -- as well as tech -- are rushing to give outside programmers an incentive to build new products and services for them. To do that, they're turning to a San Francisco startup called Mashery.

Founded in 2006 by Oren Michels, Mashery is helping about 70 companies share their inner software workings with outside developers, who in turn can use that information to build tools and products more quickly and cheaply than the companies could on their own. "Most companies don't have as their core competence running a Web site or developing user experience," says Michels, whose clients include the New York Times, Netflix, Best Buy, and Nielsen-owned Billboard magazine.

A Boom in Open Web Platforms

Open platforms, pioneered by such Silicon Valley giants as Amazon, eBay, and Salesforce.com, have been around for years. But the number of open Web platforms, called "application programming interfaces" or APIs, rose to 1,400 in August, from just 55 in 2004, according to the site ProgrammableWeb. Part of the impetus comes from companies eager to reach more Internet users in more ways, says ProgrammableWeb founder John Musser. "The future of the Web is all about decentralization -- people don't always come to you," he says.

That realization led Best Buy in January to launch Remix, a platform for outsiders to grab real-time information about the retailer's pricing and inventory integrate it into other sites. Now, customers find Best Buy products on sites across the Web, such as Camel Buy, which sends alerts to thrifty customers when certain products get marked down.

At a time when C-suite executives are tightening research...