I personally recommend
IACE for plane tickets. They`ve always been the lowest when I`ve bought tickets for myself and my family. They generally have price lists up for departures from different cities...
But if you`re planning on a trip in December, I doubt you`ll be able to find any reliable information on the cost of a ticket. Usually they only sell them a few months in advance.
I don`t think anyone would look down on you, unless you`re running around on street corners screaming that Bush is king of the world, etc. But even then, they`d look at you as if you were insane... So I doubt you`d be looked down on.