Skype have just released v1.0 of their VoIP software for Mac OS X. This is the first full-featured release on OS X, although looking at the Change Log there hasn't been that much done since the 0.15.0.4 Beta. However, this does mean that we're feature complete with the Linux and Pocket PC clients. Predictably the Windows client is at v1.1, although I'm not sure what extra features this gets you.
Skype is pretty much the best VoIP software I've found to date, especially since it's so platform angnostic. However, despite their "it just works" claims, I've had trouble pushing a Skype connections through firewalls. So, as always, your mileage may vary...
