I tried out an add-on called Perfect Raid last night because my priest friend so highly recommended it. I must say it ROCKS. It puts everyones health/rage/mana bars into one column, and you have some control over who goes where. It puts "aggro" in red letters on anyones bar that currently has aggro. For druids, an M is next to anyone's bar that currently does NOT have mark of the wild, which is great for spot buffing. Healing over time spells also appear next to names, with different colors so if everyone's taking a lot of damage and I'm throwing around lifeblooms, I know who still needs one and who doesn't.
I love it. When I'm healing the raid (and tree druids usually are), having everyone's name lined up like that makes it easy to determine who's health is lowest and needs attention the most. You can also choose to have a small number inside the bar showing how much health they need, which is great for choosing which heal to toss.
It's basically a great add-on that made healing 25 mans so much easier on me. You can find it here:
http://www.wowinterface.com/downloads/fileinfo.php?id=4673