Skype. Hands down, no contest! What do I love about it? First, it is free skype to skype. Second, the call quality is great, even between the US and India. Third, sharing files was as simple as dropping them into the window. I would love to test this out on a bigger audience, perhaps doing a presentation using skype. Since you can share your desktop (so that others can see it), it is a great way to lead a discussion. What are the benefits to using another system?