Mymail-Crypt for Gmail is a browser (Chrome) extension that brings OpenPGP support to gmail. It aims to be a simple solution to mail encryption.
It is important to familiarize yourself with Options page, where keys will be loaded and other options set.
I sometimes post about this project at prometheusx.net.
Additional help welcome. If the changes you're interested in making are in the OpenPGP component, please take a look at OpenPGP.js.
See LICENSE file for licensing info.