So, it's still pretty simplistic yet, but keep an eye on
Google Talk, as I fully expect it to become the IM protocol of choice very soon. I assume it'll support ICQ/AIM/MSN/Yahoo/etc. shortly. I'll keep y'all posted. It runs on the open source XMPP (Jabber Protocol). It integrates well with gmail. It does voice chat quickly and easily. So far my only complaints are the kinda big logo, and lack of auto-hide options. Still, looks promising. It's only been available for less than 24 hours...