TeXZilla by Frédéric Wang, Raniere Silva

This is a simple add-on adding a widget to open a tab with a local version of the TeXZilla parser. This might be convenient to use this parser offline. Note that such a TeXZilla input box is available in recent versions of Thunderbird and SeaMonkey.

You might want to install MathML fonts for best MathML rendering as well as the MathML copy add-on to copy and paste the MathML output.