Riff

f is a social network for videos developed by Facebook that allows you to create short videos and share them with all your friends in a matter of seconds. And, what's even better, it lets them respond to you with their own videos. Riff's functionality is very simple: you can create a video and add a series of tags to it so that any of your friends can respond with a video of their own. They are able to add new tags to the video they have created. So, getting passed from friend to friend, a video can get sent a long way. In addition to creating videos, users of Riff can check out the most popular videos created by other users or friends. And, of course, if one of these videos inspires you in some way, you can respond by making your own video. Riff is something of a small, video-based social network that allows you to share short clips in only seconds. And who knows, it may even help you make some new friends.