Slide, a company that develops software for social networking sites such as MySpace and Facebook, had closed a $50 million institutional financing round, Reuters reports.

Founded in 2004 by Max Levchin, Slide is based in San Francisco and it is considered one of the largest developer of third-party applications for Facebook.

Max Levchin is better known as the one of the co-founders of PayPal in 1998, immediately after graduating from college. He sold it four years later to eBay for more than $1.5 billion at the age of 26.

Slide gained an investement of $20 million in November 2006 from Khosla Ventures, BlueRun Ventures, Founders Fund and the Mayfield Fund. According to Reuters, the new investors in Slide are Fidelity Investments and T. Rowe Price.

Slide's products - including Slideshows, FunWall and SuperPoke! - are popular on top social networking and blog platforms, including MySpace, Facebook, Bebo, Hi5, Friendster, Tagged and Blogger.

Slide is also the leading developer on Facebook with more than 84 million applications installed and the most active users than any other developer.

According to the Slide’s website, the company reaches 144 million unique global viewers each month and more than 30 percent of the U.S. Internet audience.

Slide’s main competitor is a Rock You, a company founded in 2006 and backed up by investors

such as Sequoia Capital, First Round Partners, Lightspeed Venture Partners, and Partech International.

RockYou widgets include photo slideshows, glitter text, customized Facebook applications and voicemail accessories.

Last year, Facebook announced a major change, Facebook Platform, a new development platform that enables companies and engineers to integrate with the Facebook website and gain access to millions of users.