Move the tab bar - Firefox

Use the ChromEdit extension to edit your userChrome.css file to add the code you need, as follows.

Move it to the Bottom

/* Display the tabbar at the bottom */
#content > tabbox {-moz-box-direction: reverse;}

Move it to the Left/Right Sides

/* Display the tabbar on the left */
#content > tabbox {

 -moz-box-orient: horizontal;

}

.tabbrowser-strip {

 -moz-box-orient: vertical;
 /* note: you can set this to -moz-scrollbars-vertical instead,
    but then the scrollbar will *always* be visible.  this way
    there is never a scrollbar, so it behaves like the tab bar
    normally does */
 overflow: -moz-scrollbars-none;

}

.tabbrowser-tabs {

 -moz-box-orient: horizontal;
 min-width: 10ex;   /* you may want to increase this value */
 -mox-box-pack: start;
 -moz-box-align: start;

}

.tabbrowser-tabs > hbox {

 -moz-box-orient: vertical;
 -moz-box-align: stretch;
 -moz-box-pack: start;

}

.tabbrowser-tabs > hbox > tab {

 -moz-box-align: start;
 -moz-box-orient: horizontal;

}

/* remove the close-tab button */ .tabbrowser-tabs > stack {

 display: none;

}

If you want to move it to the right, add the following lines to the above:
/* Instead, display the tabbar on the right */
#content > tabbox {-moz-box-direction: reverse;}

Unabashedly stolen from James.