Have you tried Skype yet? It’s an internet-based phone service. Seems to be best for international calls, but should work fine for standard calls. My Skype ID is: fheald.
Now, of course I’ve got suggestions. It works on the Mac (yay!) but it doesn’t integrate with iChat. Yet. That’s probably up to Apple to implement, but I’d sure appreciate it if all these disparate messaging applications could be integrated. (When Apple knows something should be built but they can’t be bothered, they refer to it as a “Third Party Opportunity.”) iChat itself is actually using the AIM protocol — which is why my iChat ID is: justfredol.
I’ve been collecting all these on my contacts page, which I now realize has been semi-broken for who knows how long.
The problem with messaging in 2004: I have a phone number, a Skype ID, an iChat ID, an AIM ID, and an email address. None of these talk to each other unless someone makes them. It should be one thing. It isn’t. It won’t be for a while.