Note: This addon REQUIRES you to have LibSlash installed! You can download LibSlash from the WAR section of Curse: http://war.curse.com/downloads/details/13510/

Vertigo allows you to customize action bar layouts - set the number of columns, the number of buttons on the bar, show/hide the pagers or background for each bar, and whether or not to show empty slots.

Example usage:

/vert cols 2 1 (sets bar 2 to 1 column, i.e. vertical)

Use /vert or /vertigo in-game for a full list of options.