You can put spells like Divine Hymn on your action bar and see their cooldowns, or use other addons to do so. One addon for doing this is Power Auras. Even though I've used it for a long time, sometimes getting it configured properly seems a little tricky.
I'm going to go through an example with PoM, where I position the information directly above my raidframes. That way my eyes don't have to travel down all the way to the action bar (ability should also be on action bar for sensing usability). I've also added additional conditions which you will see.
Here is the basic setup which shows a PoM icon above my Raid frame when it is able to be cast by me.
Ok, that's pretty useful for me, but PoM is a unique spell. Even though it is able to be cast, I may not want to cast it until it has timed out or used up its charges. Below I've overlayed some text on top of the icon to show me that information. I've done this by defining a 2nd aura for PoM, and placed it on top of the 1st.
The other thing I can think of that might be cool, since we've gone this far, would be to add another text overlay for when PoM is on me. I could indicate in Text that SW Death is needed to send it on its way, or simply say "Do it" again to prompt me to recast it on the tank. Here's the settings after I got that working.
I hope this gives you some ideas for other uses. Some that I have used are indicators yelling at me that I was Positive or Negative, or that Spell Reflect was active.
Please note that it is very useful to copy a working aura of the type you need. Simply select the aura that is working, press the copy button, then select Page 1 to put it on the same page of auras. Then you can modify it.
I hope this will get you thinking of uses, and perhaps you will find it as handy as I have.
Edited, May 16th 2010 2:29pm by dadanox