Leigh , at TALO has reviewed Gizmo – a VOIP application, that he feels has more to add to educational uses of VOIP than, say Skype, which is generally the most used. I like the links to Google maps that it has, and you can IM as well as talk. (Though I can’t see the option for Video – nor does it seem that you can VOIP to more than one person at a time.)
The ability to save conversations is useful – there are pros and cons of voice and IM as far as I can see:
Voice – there’s no easy way to find a particular section again – though, unlike a classroom, it’s easy to record, so the possibility of going over something exists. It’s generally 1:1
IM: The transcipts generally make finding a particular section easy; but, typing isn’t as easy for most as talking. You can have as many people as you want in a discussion. (Not sure if that applies to Gizmo, as I’ve not tested it yet)
Given that I haven’t tested it, I’m also not sure about the firewall issue, for those behind firewalls.
Another useful tool is Google Talk, though that’s just text based & you have to have a gmail a/c. But, it’s nice and small.