I know it's not the go-to option, but for me Button Forge has become absolutely necessary to my play style. It lets you create and resize fully customizable action bars. You can have many of them with as many slots as you like. They can be set to come up when you're in a vehicle and change with your spec. The best part is that they can be bound to any key, or combination of keys you like. The way I'm doing it is I have a mouse with two thumb buttons which I have set to shift and control respectively. I will then use WoW's key binding to setup combos particular to an action-type. For instance, I main a Prot Warrior so I have my first six number and F# keys bound to common abilities.I have a row of bars above that which are bound to the shift and control mouse thumb buttons, with my defensive cool downs bound to the shift combos, and health regenerative skills bound to the control combos. This makes movement in-battle so much easier to handle, and it allows me to organize my skills in my own mind in a very logical way that's easy to recall even in the thick of a difficult raid encounter.