ishowu for the mac is pretty cheap. i am afraid there aren't too many free options that are easy to use. there is http://www.unixuser.org/~euske/vnc2swf/ i've used it before, but honestly spending a few bucks in this department will save you time in the long haul.
there was some sort of hack with using yui as a guided tour a few weeks back, sorry no link. applying a voiceover could be a problem though.