Define your own shortcuts to move the tabs into firefox
Since Firefox 3.5, move a tab in the tab bar using the keyboard became a problem. You must have the focus on the tab bar in order to make the shortcuts Ctrl Left and *Ctrl Right work, and click is not enough. To do so, the easiest way is Ctrl k to focus the search toolbar then Tab to focus the tab bar. This "solution" is just a work around, and a little bit too complicated to only move a simple tab.
This plugin allows you to choose your own shortcuts to move the tabs. You can move the tabs along the tab bar and at both ends.
Defaults shortcuts are: