If you can't, for any reason, convert to FLV and put up a Flash player, upload the screencasts to Vimeo (http://vimeo.com http://vimeo.com), skin the player and

If you can't, for any reason, convert to FLV and put up a Flash player, upload the screencasts to Vimeo (http://vimeo.com http://vimeo.com), skin the player and embedde it on your site - you'll get better quality and will look more professional than a YouTube solution