Probably one of the most useful thing that I’ve discovered this month:
http://sourceforge.net/projects/pidgin-latex/
Pidgin-latex lets you write Latex code normally in your chat conversation and renders the result in real time.
For both parties to be able to see the result, they will have to install this plugin or any other one that is handling the mime type latex.
To switch to math mode, it suffices to enclose the content between “$$” symbols.
The install process is straightforward. No trick needed. Just follow the one line instruction from the README.