Hardware only method, involves having one computer per Instance of WoW.

Then people usually have a single wireless mouse, and a wireless reciever for each PC. There are some issues with it, diffrent resolutions, diffrent mouse speeds, even down as far as how close the wireless recievers are to the mouse thats controlling them.

It is the most effective way we've found for using the "click" spells, but unfortunately, is only viable for the 'elites' amongst us. :-)