"Packages" can't be reserved until the 2009 rates are unveiled, which, as stated earlier, will likely be some time in August.
But you can book a "room-only" reservation right now! But only by telephone, not on the website. In fact, you can make room-only reservations 499 days in advance.
If you want to stay in a resort or room category that frequently sells out, then you definitely want to go ahead and book a room-only reservation ASAP, to make sure you aren't locked out of getting the room you want. You can change it to a package later, if you want.