I use Need to Know for timer bars for buffs, debuffs, and cooldowns. There are a few other addons that do the same type of thing. Need to know is easily customizable for all your classes though.
It's nice once you program yourself to recognize a color almost running out translates to using a certain spell. You won't even need to look at it other than the corner of your eye once you are used to it.
Leafkiller and Aggixx have done a lot of work on it. The latest script is available with the "Nerien's Ovale Scripts" add on. When Leaf makes any changes the addon will be flagged as an update (curse client). You can find it here. We also have a Q&A thread for the script at Fluiddruid.net.