I saw the following on Orbitz today for Pop Century. I don't know if it applies to any other Disney hotels.
Orbitz Special Offers for Disney's Pop Century Resort
See below for promotion(s) available for this hotel
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Rates starting from $59.00
Terms and Conditions Book 8/28-9/27/08 for stay between 9/28-10/11/08.
Fulfillment requirements Book 8/28-9/27/08 for stay between 9/28-10/11/08.
Valid for stay between 09/28/08 - 10/12/08
Minimum length of stay requirement - 1 day