Parse the XMPP chat protocol (also known as Jabber XML Messaging).
Example traffic can be found in the "2009 Inter-Service Academy Cyber Defense Competition" dataset collected from "Outside West Point Network Border":
http://www.itoc.usma.edu/research/dataset/index.html
More info on applications and systems that use XMPP:
http://www.internetdagarna.se/track/media/social-computing-or-let-the-bots-talk
It seems as if Google Wave also is based on XMPP. More details here:
http://www.process-one.net/en/imtrends/article/google_wave_another_steps_toward_xmpp_powering_the_real_time_web/
Also look at Apples XMPP usage and what ports they use:
http://support.apple.com/kb/ts1629