Camtwist is a nifty Mac-only add-on that allows you to also stream your desktop, presentations, pictures, and movies within Ustream. Download Camtwist, install it, and restart your computer. To stream your desktop or movies, first start Camtwist followed by Ustream.

START Camtwist, and select from the following input sources: webcam, desktop, slideshow, movie, or Flickr Set.

Within Ustream, switch from your camera to the Camtwist feed by pulling down the VIDEO SOURCE menu and selecting CAMTWIST.