I am not sure about what airport you fly from, but we usually use Philly, so our choice is pretty limited to USAir. I suggest booking as soon as you get a price you can live with. My safe price is $200.
For our July 2003 trip, we decided to go in February. I wanted and waited and ended up booking when prices dropped to $225 in early April. I kept checking, but they didn't drop any lower.
For our December 2003 trip, I booked at the end of April when the price dropped to $204. It has steadily increased since then, and is around $400 right now.
For our June 2004 honeymoon, I booked in August as soon as they released the rates for those dates. We are taking a cruise, so we had to take one of the first flights out, which limited our choices. I got the tickets for $201. I keep checking, but they are hovering around $206 right now.
I don't think that the airlines are following their historical pricing schemes right now. Because of codesharing, if a flight doesn't book up, they cancel it and move the people to another flight instead of lowering airfares to fill the plane. So, I would book as soon as you can. We are pretty picky about the times (ie leave very early, return very late) so as soon as it gets close to $200, I grab it. I figure it isn't going to go much lower than that anyways, and at least I don't have to stress out about it anymore. Good luck!