The main 3 healer addons are Vuhdoo, Healbot, and Grid. I use Grid, but that's mostly because I've already gone through the pain of setting it up the way I want, but it's not very user friendly. I've heard good things about Vuhdoo and Healbot, and they're supposed to be much easier to learn and setup from scratch.
Clique is an addon that makes it easier for you bind specific spells (heals) to mouse buttons. It's not a UI addon, per se.
If you want to keyboard-press your spells (1-5, or whatever), and hover over UI to heal your party without needing to select them, you can create mouse-over-macros.
It really comes down to how you naturally steer your character.. whether you do WASD or if you use your mouse to move. If you use WASD to move around the screen, then you'll probably want to go the clique-route of binding spells to SHIFT, ALT, CTRL + mouse buttons. If you move with your mouse, then you'll probably want to go the mouse-over-macro route.
Here's what all my mouse-over-macros look like (There's a decent explanation over here:
http://www.worldofmatticus.com/a-guide- ... er-macros/ ):
#showtooltip
/cast [target=mouseover,help] Lifebloom; [help] Lifebloom; Lifebloom
Replace Lifebloom with whatever spells you want to cast, and then replace the old "Lifeboom" spell on your action bar with the new macro.