ScreenCamera is the CamTwist for Windows. ScreenCamera allows users to stream the desktop inside video conferencing programs and websites such as Skype, Live Messenger, Yahoo Messenger, AOL Messenger, blogTV, Justin.tv, Mogulus, Ustream, and so on.
ScreenCamera can also connect to your Webcam and stream both Desktop and Webcam at the same time.
It works with a video resolution of 640x480 and it is hard to find something not to like about it. It is cheap and to me it is a must have tool for video conferencing.
You can download ScreenCamera here:
http://www.pcwinsoft.com/screencamera/
http://www.pcwinsoft.com/screencamera/download.asp
Best,
Alex