Team liquid is what I think of when I think of active moderation done right
Those guys and the DAD clan from TFC (now disbanded) had some of the greatest mods. They kept the places in check but they had a sense of humor about it.
[1] - http://www.teamliquid.net/forum/tl-community/17883-tlnet-ten...
[2] - http://wiki.teamliquid.net/starcraft2/TeamLiquid.net_Staff