Inserting and collaborating on formulas in Etherpad is really easy by simply installing the ep_mathjax plugin.
What are these things?
Etherpad is an open-source collaborative editor.
LaTeX is a high-quality typesetting system
Getting started with LaTeX and Etherpad
To install the plugin browse to http://youretherpadhere/admin/plugins and install the ep_mathjax plugin
Once the plugin is installed click the ∏ button and you can begin writing LaTeX Markup. Submitting the form will insert the LaTeX representation of your text into the pad.