So, I thought I'd bookmarked it, but apparently I haven't. It was, if memory serves, a Health and Energy/Rage/Mana/whatever mod, and it made them into rather flashy-looking circles. Any help is hugely appreciated.
Did they completely replace the Unitframes? If so, you could try checking the UnitFrames addon section on WoWInterface - Unitframes or on Curse - Unitframes.
Can't think of any addon that you've described...