Skype would also be a wonderful way to have an author discuss their work. Or to have an expert on a subject (ex. a paleontologist discussing bones) to bring it closer to our students.
I checked out the other skype-like programs and found the original to be the most user friendly. Of course with practice, teachers and students could become adept at using different products. I think Skype and similar-type products give students hands on learning which sparks their interest and peaks their higher-order thinking skills.