I was working on a macro for my disc build that would allow me to smite while healing without having to target the mob, and here is what I came up with.
/cast [target=mouseover,harm] [target=target, harm] [target=targettarget] Smite
Basically what this does, if you target your tank, you will smite whoever the tank is targeting. If you target a harmful mob it will cast smite, and if you mouseover a harmful mob it will also cast smite (useful for picking off runners). With train of thought, this is awesome, just target your tank, spam smite, shield and penance the tank, and penance cooldown is up in no time. I think I will make a mouseover macro for renew and flash heal as well.