Gizmo
I ran across the Gizmo Project today. It warms my heart. Now that I have cultivated your curiousity, Gizmo is what Skype should have been. In other words, Gizmo is Skype with standard open protocols. (SIP, to be specific)
It was easy to set up Asterisk, and I have bidirectional Asterisk-to-Gizmo communications. The one caveat is that I can't seem to call my Asterisk box from my Asterisk box via Gizmo. I'm not sure why that is, but aside from testing that wouldn't be all that useful so I'm ok with it.
My only complaint is some clown stole the username I prefer. So, on Gizmo I guess I go by hans_fugal (17476265435). Give me a call! Or, at least, give my monkeys a call.