I like Asterisk. It's a VoIP telephony PBX with a tremendous amount of features. Still, there are always things it can't do. Fortunately, they have the Application Gateway Interface, AGI for short. This interface makes it possible to script Asterisk with, for instance, Python.
On this page, you find the AGI scripts I created for my Asterisk server. As usual, those are all licensed under the GPL. At this moment, there is only one script, but the page is bound to be extended in the future.
Jabber
With this AGI-script you can have Asterisk send Jabber messages. It uses sendxmpp, so make sure you set that up first. After that, you can use the following in your dialplan to send a Jabber message:
exten => s,1,AGI(jabber.agi|you@jabber.org Hi there)
Just download the script, and place it in Asterisk's agi-bin directory. You also need to install pyst, the Python AGI interface.
Download jabber.agi.