Services like Ustream.TV, Justin.TV, and Stickam.com are no longer limited to streaming the signal from your web cam thanks to CamTwist. This free software will turns your desktop, a slide show, or a video file into its own virtual web cam.
The software—available for Mac OS 10.4 and above—presents the user with a variety of options for video sources. Effects can then be added to these sources—though I can’t imagine much use for these effects beyond mere amusement. From there, CamTwists video feed can be accessed just like any other web cam.
The software also works with popular chat clients like Skype and Yahoo Messenger, allowing you to integrate screencasting or media files into one-on-one communication as well. Online training sessions or video conferences become much more rich and interesting when this sort of media can be integrated smoothly. Note that iChat is not yet supported.