World of Warcraft, you won't be finding them. As our sister site WoW Insider has found, Blizzard has temporarily shut down the arena servers.
The problem seems to stem from the ratings calculation system, which seems to be generating inconsistent results. Until this problem is resolved, arenas will be remaining offline. This is, of course, in addition to all the other bugs that have been introduced with patch 3.0.8, including the bug that has caused Blizzard to completely close off the zone of Wintergrasp as well.
Currently there is no estimated time for the arenas to come back up, but we'll keep you informed as to any breaking developments.