My apologies to the vim contingent for dragging emacs out into the light again, but it’s pertinent and it starts with the letter J: jabber.el.
In AUR as emacs-jabber, this implants a jabber-based messaging client inside emacs. Good grief, is there anything emacs doesn’t do?! 😉
By most accounts this has been around for a while and I had only moderate difficulty setting it up; the instructions for 0.7.90 on this wiki were very helpful. Without them, jabber.el could never connect to the Talk server. 😕
Beyond that, as you can see, I didn’t do much to add contacts. Mostly because I wanted to see if I could spawn a black hole by telling emacs-jabber to connect to myself.
No such luck. I guess emacs doesn’t do everything … yet. 😯 🙄
Inconsolation 
Hardly anyone uses Jabber, unfortunately. The only major user now (in my circle of friends at least) is Facebook, and the online client is much more powerful. I just keep Facebook open instead of using this, as much as I love me some Emacs. All my other friends are on Skype, which uses a proprietary protocol (that’s surprisingly good; even the Linux client).
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