Skype is an Instant Messenger client with a twist — if you hook up a microphone you can CALL each other. Like a telephone, only you can see if your buddy is online before you interrupt them. The audio quality is very good, and clients are available for Windows, OS X, and Linux. The Linux client works on FreeBSD.
Even nicer, you can dial out on Skype, for exceedingly low rates. It costs us about 3c a minute to call Japan, though we’re going to get Noriko-san on Skype soon enough, and then the calls will be free.
If anyone wants to try it out, you can ring me at dannymanTM.
To answer a question you may have on your mind, Skype is not a telephone, so it is different from a VOIP service, where they send you a telephone that you hook up to your broadband. Instead, Skype is a way of making telephone calls from your computer. Unfortunately, people can not yet dial in to someone using Skype.
For me, though, it is as if the Internet has come full-circle: we used to have to find a cheap local number to dial in to the Internet on our existing telephone. Now, we are finding cheap services to make telephone calls on our existing Internet connection. Yow!