I’ve used Skype before. It’s a great idea and keeps the cost down when communicating internationally. Also used instant messaging both in a personal capacity (msn version and via facebook)) and a professional capacity (groupwise has an instant messaging capacity) and think both initiatives are great.
While I was with a previous employer, I was working within a network with multiple campuses. We regularly held remote meetings using Instant messaging. It was a very efficient means of coming together to share ideas but not having to suffer the inconvenience of travel.