What TDC Nala said is right...but it should be pointed out that the UK got a larger window in 2008 than those of us in the US did...expect
free dining to have a similar window next year...FD bookings will be opening in early April.
Also, to answer a few previous questions:
1) Yes you will need to give a $200 deposit to book bounce-back if they offer it....last year you had to book by Sept 28th. The bounce-back window was only 9/1 -9/20, while the final dates were 8/24 - 9/20. (Note you can, at least in '08) arrive on the last day of FD and extend it up to 10 days - so you could book 9/20 - 9/30 on FD is you needed.)
2) There will be free dining to the general public next year...and there will be panic on the DIS for 2 months leading up to it until the announcement is made. Expect a similar deal as in UK next year - values and mods will get the QS dining plan, while only the Deluxe get the regular DDP. (Yes, they will have values on the US FD next year.) That is all guesswork on my part, but I'm pretty smart. Just ask me.

Seriously, I've watched this unfold for 2 years in a row and now know the drill. (Though we will not be using FD next year.)
3) If you book a room-only reservation for next fall, and then want to change it to the DDP, you will actually have to re-book a package and cancel your original reservation. If you pre-book a package, even if you don't initially book the DDP, you can add free dining without changing the reservation.
4) Pay attention to other deals - FD is not always the greatest deal because you have to pay full-price for your room. 40 % off in a moderate, or 25 % off in a deluxe can be a better deal than free dining.
SkierPete