If speaking about working on live servers, there is the aforementioned
OptionHouse (on
Github too), which is my favorite.
One small issue with it, though. When you loot/skin/open a mailbox or vendor (or AH, etc.) frames, the panel for OptionHouse shuts off. You have to restart it after opening those frames. Which can make it hard to see how much CPU a mod is using when opening those things.
My two other favorites (working on live) which I use when I need something that doesn't close when opening those frames:
Addon Profiler (on
Github too) &
Addon Manager. Unless you are speaking of some other "Addon Manager" or using on the Cata beta, that works just fine here.