Check the Twitter and Facebook plugins for examples of the state of the art of a ThinkUp plugin.
A plugin is located in
/path/to/thinkup/webapp/plugin/pluginname/. Some notes on directories within a plugin directory:
assets: Like the main webapp, assets is where you store images, CSS, and JS for your plugin.
controller: This directory contains the guts of your plugin, and all PHP files in this directory get auto-included in ThinkUp at runtime. Here you define the functions that run your plugin, and register them with the
tests: All your plugin's model and controller methods should have regression tests. Include the tests in this directory, and any test data in the
view: Your plugin's Smarty templates live here.