Facebook’s move last month to open the inner workings of its web site to outside programmers has sent ripples through the Web 2.0 world, as entrepreneurs rush to build services that take advantage of the connections between the site’s millions of users.

By allowing outside companies to integrate their features with Facebook’s messaging infrastructure and other services, Mark Zuckerberg, the company’s 23-year-old founder, is attempting to transform Facebook from a social networking site into a springboard for launching internet applications.