How would I change the default widget list.
Specifically I would like to change some of the options in the popup menu when you click the add widget option.
Please advise thank you.
Change?
Go to Settings | Plugins Management. On this tab, you can activate /deactivate plugins (and associated widgets).
Go to the Developer Zone (dev.piwik.org) to learn more about the API to create your own plugins/widgets. There are also a few third party plugins in Trac.