This is a TBC backport of "Simple Action Sets" (from Wrath of the Lich King), along with tons of important bugfixes.
It is without a doubt the best addon for saving and restoring your actionbars, and has a great GUI which allows you to choose exactly which bars and buttons to save and restore (all bars and buttons, or just a few), and lets you view the contents of your saved sets without restoring them. It is much, much, muuuuch better than the absolute-garbage "ActionBarSaver" addon which people usually use (which lacks a GUI and has no fine-grained controls whatsoever).
Swapping sets is incredibly easy. Just open the GUI, select the desired set and apply it. Or right-click on the minimap button and apply that set. Or use the command-line control, such as /sas swap <setname> to quickly swap sets (can be used via macros).
So what are you waiting for? Download Simple Action Sets and try it out! You'll wonder how you ever lived without it!
Requires World of Warcraft - The Burning Crusade! (TBC 2.4.3)
Download: SimpleActionSetsTBC-master.zip (Put the inner "SimpleActionSets" folder into your WoW's "Interface/AddOns" folder.)