UpdateOk, theyve officially announced the testing of the prototypes directory now.

From the company blogFacebook Prototypes let us share the experimentation going on inside the walls of Facebook with the rest of the world. Youll be able to test any of the products and features we launch as Facebook Prototypes and then provide feedback directly to those of us who built them. To access Prototypes, visit the Application Directory and filter by Prototypes. From there, you can activate or download any of the Prototypes listed.