Due to how popular Digg is, you would think there would be more Firefox extensions related to it. I just have not seen too many become too popular. The Digg This! Firefox extension hopes to change all that.
The Digg This! toolbar adds two buttons to your main Firefox toolbar and one menu. With the toolbar buttons you can quickly goto to Digg or Digg the page you are viewing. The menu allows you to goto your Digg profile or any of the top Digg categories.
If you do a lot of digging, then this extension is right for you.