At the Social Good Conference on Friday, marketing/outreach director Randi Zuckerberg announced Facebook would be opening its new "credits" platform to four non-profits: Project Red, Toms Shoes, Kiva and the Wold Wildlife Fund.

The non-profits add to the four online gift and greeting companies that were invited to try the platform last week: American Greetings Interactive, GreetBeatz, Someecards and Real Gifts.

"We are exploring ways for developers to use the Gift Shop to offer…virtual, real, and charity gifts," Randi Zuckerberg said, adding that if the pilot proves successful, "we may open to everyone really soon after that."

The eight companies — four non-profits, four gift firms — will be selling virtual gifts on Facebook, in part to test the socnet's new "Pay with Facebook" virtual currency. The company began privately testing the currency program in June, in hopes that a universal payment system would make it easier for users to make purchases, as well as for vendors and Facebook to profit from those purchases.

The use of "credits" is also intended to make the payment system more global e-commerce friendly; prior to this, the site only dealt in US dollars.

According to C|Net, Facebook first offered "charity gifts" for 48 hours when it crossed the 200-million-members milestone. 16 non-profit organizations and advocacy groups participated.

The new system rolls out this week, Inside Facebook writes.

In late July, 1-800-Flowers made it possible for users to order floral arrangements directly from Facebook.