The Custom Buttons² Firefox extension provides the code base support necessary to create, maintain, import, and export custom toolbar buttons. The buttons can perform just about any task, with a large number of buttons already available on the extension's forum.

Custom Buttons² extension buttons can be written to do various tasks that the user may require. The buttons are coded in JavaScript. Many bookmarklets can easily be converted to buttons.

Extension developers will find this extension quite useful in the development cycle. JavaScript code can be prototyped in a custom button, avoiding the reload chrome step until the code is proven. Then the code can be moved to the extension.

Buttons Database
Buttons Database (Alphabetical List)
Custom Buttons² Documentation
Extension Releases and Issue Tracking