http://dialog.gs/
I’m a little embarrassed to admit that I still use Google Wave, namely for chatting. I like how it has less overhead than email, yet doesn’t demand attention like iChat, which disrupts my workflow. That said, it doesn’t exactly feel like it was designed for person to person chat, and I’ve been waiting for another service to convince me into leaving. I don’t want to get my hopes up, but Dialoggs looks like it’s moving in that direction.