We've known for a month that Facebook is working on a new HTML5-based app store that it's calling the App Center, for both desktop and mobile, and now more screenshots have leaked out surrounding this major new initiative. TechCrunch is reporting that Facebook has been testing the App Center with a "small percentage of users" and some iOS screenshots it received appear to be from that test.
Unsurprisingly, it looks like you access App Center from the left navigation pane, where basically every other navigation option is currently held. You can navigate through "social picks" (based on what your friends are using) as well as "top apps" that are determined by Facebook. Tapping through to an app itself shows you all of your Facebook friends who have it installed — one of the more useful features of this store, and not something that is currently supported by Apple or Google. Facebook plans to hold a event tonight where we expect a formal announcement, and we'll be there to cover the news.