On the extreme minimalism end:
BasicBuffs.
Allows you to "unlock", move & "relock" the default Blizzard buff/debuff frame via a command line toggle (
/bb lock). That's it.
In terms of more complicated ones that actually allow you to click buffs off _in_ combat (as well as scaling, etc.), the choices are very limited.
nivBuffs mentioned above &
Bison are the only two I've tested that allow it.