*Update: Facebook Prototypes has now officially been announced at TC50.*

Facebook’s Twitter account has just posted a link to an image showing a new upcoming “prototypes” feature similar to Google Labs. (The image has now been removed)

We’ve emailed Facebook for comment but it’s pretty clear that the new area is a way to test upcoming features to the Facebook platform without immediately making it available to the bulk of Facebook users.

Out of the three Prototypes above, currently available to the public is Desktop Notifications, a slick Mac OSX app, initially spotted by the team at TechCrunch.

Thanks to Patrick on Friendfeed, we’ve also managed to find the two other applications mentioned below. The Similar Posts application can be found here and the Enhanced Event Emails is here. Interestingly, both of these applications are not developed by Facebook and it seems you aren’t able to add the application just yet, although you can fan and block it.

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More coming soon.