You can book award tickets on jetblue.com, without speaking to an agent. Just go to where you saw the availablity, and continue through the booking process. The way I understand it, is that you first convert your Amex points to Trueblue Points (250:1), the points are converted into an award automatically, and then you can use the TruePasses (2 per award of 100 points) to book a one-way ticket on jetblue.

There are no award booking fees, other than the Sep 11 Security Fee (or whatever it's called now) of $2.50 per segment per passenger.