Facebook posted an image earlier today and quickly removed a shot of three upcoming prototype applications via a soon to be added, Facebook Prototypes category in the application directory. The three applications include “Desktop Notifications” which many other blogs have extensively covered, and two applications never covered previously: similar posts and enhanced event emails.

The first application: “similar posts” will most likely let you track which feed stories are similar to one that you are currently viewing. The second applications “Enhanced Event Emails” includes “an iCal file as an attachment to your Event Invitation emails”, letting people put the event on their existing calendars. What’s interesting is that we can expect Facebook to roll out numerous other prototype applications over the coming months once this is added to the application directory.

The company accidentally posted the news on Twitter and on their blog but then quickly took the news down which makes us think this will go live either later today or tomorrow. Google has Google labs and with Facebook’s ongoing growth, they are looking to include an area which can let users test out some of the new features that they are working on.

Update
Facebook demoed this among other new applications at Techcrunch 50 including the following apps below:
Photo Tag Search: Find photos that include multiple friends within a photo.
Recent Comments Filter: Sorts your news feed stories based on those stories which have a lot of comments.