ScreenToaster is a screen recording site that is totally free, but you have to run java applet. It may slow down your computer just a bit. But if you download mycleanpc.com, you will get pop-ups saying this isn't a safe site if it is bad for your computer.
ScreenToaster, the Web-based recorder, no installation. or Democreator, Flash-based recorder with editing features.
Screentoaster is currently being reported as down. They are probably doing maintenance on the site. Try checking back later to see if they will be up again.
Camtasia is a pretty good screen capture program. Or you could use an online one like Screentoaster. As for exporting it as a webcam; Manycam is a webcam emulation software package. If you go into the source options you can set it to Desktop. The your screen will be exported to the Manycam virtual webcam.