In the days that we had annual passes to Disneyland but could not afford to eat out at ALL, we would pack our lunches and eat in the picnic area just outside the park. I'm not sure if any of the parks at WDW has one of these, but it's a nice shaded and secluded area with tables and soda machines just outside the main gate (most people don't even know it's there) with lockers. We'd leave our lunch or dinner there in a locker, go in and enjoy the park (bringing our own water of course), get our hand stamped and go over to the picnic area when it was time to eat, then re-enter the park. Even if WDW doesn't have a place like this in any of their parks (I bet they do), you could go out to your car or make your own picnic somewhere outside the gate in a nice area to sit.
A friend of mine who just went to WDW suggested that you would buy a double cheeseburger for one person, and then just buy a bun for about 20 cents, and in that extra bun, put the extra patty, and fill it with fixings from the burger bar, and you have two burgers for almost the price of one.
(We didn't do this, but she did, and says she saved a lot of money)
No we get into all the parks for free and get significant discounts on everything else, so that is my best money saving tip - work for Disney.
