Adium 1.0.6 saw the removal of the LaTeX plugin. Here is an Xtras form of it.
See the Adium Wiki
for how to get this plugin working.
The source for this plugin can be found in the Adium SVN repository
If you want to customize the font size of the generated LaTeX, navigate after installing to:
- Your user folder > Library > Application Support > Adium 2.0 > Plugins > Latex Plugin.AdiumPlugin
- Right click, and get "Show Package Contents".
- Go to the Contents > Resources folder, and edit preamble.tex, and edit the first line from 12pt to your desired font size.