Hi Susan,
Generally during less busy times of the year, Walt Disney World offers discounted vacation packages including Free Dining.
I would watch the
Special Offers for announcements of Free Dining packages. When discounts are released, they will include the eligible vacation dates. In addition, you'll have to book prior to the booking window expiration date.
Here's an example:
The last Free Dining offer was released on October 27, 2011 and had to be booked by December 17, 2011. Eligible vacation dates included January 8 - March 29, 2012.
I would caution that depending on where you stay on WDW property, the free dining plan isn't always your best option. Do the math. When free dining is offered, you'll pay rack rates for your hotel. If you are staying at a value resort, free dining is more valuable. If you are staying at a deluxe hotel, it may be more cost-efficient to get a discounted room package and pay out-of-pocket for your meals.
Another great resource for information on discounts at WDW is www.mousesavers.com. I visit this site to find discounts on my Disney vacations!