Nov. 28--They crowd the lobby of Google's Building 43 one evening a month, waiting to climb the wide stairway under a mock-up of the world's first private spacecraft, SpaceShipOne, prepared to delve deep into the Internet giant's brain.

Over the next two hours, they will get a lecture about Google software, along with a free, catered dinner in this sanctum sanctorum of the Web. But the 30 to 100 software programmers who regularly attend the Google Technology Users Group don't even work for Google -- at least, not directly.

"You want to build something to help people, to make money, to become famous -- for all the right reasons," said GTUG member Siamak Ashrafi, explaining his passion for software applications that allow smart-phones equipped with Google's Android operating system to become a kind of personal medical assistant.

When Facebook in 2007 began allowing independent developers to write software applications that ran on the social network, the response was immediate -- the site now features games and other software applications by more than 1 million programmers and entrepreneurs from more than 180 countries. Now Web portals like Google and Yahoo, telecom companies like Sprint and smart-phone-makers like Palm, and even providers of online services like PayPal and LinkedIn are scrambling to position themselves as open platforms where highly motivated, independent software developers like Ashrafi can build and market their software

-- known as "apps" -- to the world.

In turn, those apps woo Web traffic and consumer interest back to the platform, the way flowers attract honeybees to their pollen.

The popularity of Apple's iPhone and its more than 100,000 apps that allow users to check everything from surf conditions to a bank balance has accelerated the trend.

"It's a paradigm shift in how companies deliver value to their customers. Instead of trying to do it all on their own, it's solidifying this very motivated group of developers -- even more motivated than an employee in many cases -- to go after a large number of ideas in a very effective way," said Osama Bedier, vice president for product development for PayPal, the San Jose online payment service that opened its platform to third-party developers this fall.

"Imagine if every app on that iPhone had to be built by Apple," Bedier said. "I don't think the physics of that would make it possible." Typical of its culture, Apple keeps a tighter rein on those apps than many of the open-source models used by companies like Google.