WDW has several levels of resorts ranging from campgrounds to deluxe. Each has a pricetag to match. If you enjoy camping, you can pitch a tent for as little as $41/night. Or if you like luxurious surroundings, it can skyrocket to over $300.night.
WDW also has between 4 and 5 "seasons", depending on what level of resort you're staying at. The most affordable season at any resort is "Value Season" and its dates vary by resort. For the campsites, Value Season runs from January 1 to February 14, and again, July 29 to November 15 in 2007. For Deluxe Resorts, it runs January 1 to February 14, July 8 to October 3, and November 25 to December 19.
Passes cost the same, regardless of the time of year. Sometimes Disney will offer a promotion on packages which will give you added features on your pass (such as free waterpark admission or park hopping option). If these are features that you would take advantage of, then they can be a money-saver.
Disney has also offered "
free dining" in the past. While you would still pay the standard rate for your tickets and an undiscounted price for your room, the amount of money that your family can save on food costs can be worth it. The free dining offers in the past have occurred during Value Season at most of the resorts. Last year it ran during the latter part of August thru the end of September. There's always the possibility of them offering it again this year. If I had the flexibility to choose my dates, I would set my sights on that time of year for a possible trip.