Witivi is an interesting project from Collabora, it’s a real time HTML5 video editor. It’s currently in a pretty early development stage but there’s plans on supporting transitions and other cool effects you’d expect from a video editor.

For a demo and more information check out this blog post.

http://mbatle.wordpress.com/2011/11/02/illusions-in-the-web-a-real-time-video-editor-built-in-html5/