"Why not just use Skype?" I get this question all of the time; my answer is that if Skype meets your classroom needs, then go ahead and use it, but there are reasons to use a videoconferencing system instead of Skype. The following PowerPoint gives an overview of the pro's and con's of Skype vs. Videoconferencing (thank you to Janine Lim and her great blog VC Out on a Lim):

Skype vs. Videoconferencing