As of August, all fares were quite high, presumably due to fuel prices. I've seen some extreme discounts over the last 5 weeks or so after oil prices dipped into the mid $80's.

I book most of my travel on Southwest, where I can re-fare downward and keep the difference for future use. The lowest fare tends to be 8 to 12 weeks before travel unless fuel costs change dramatically. On some other airlines you can get a cheap seat far in advance, but I believe other airlines are beginning to copy Southwest's tactic of not offering the lowest fares until closer to travel date, reducing the fuel cost uncertainty for the airline.