Look at the savings that a AAA membership may get you. Even if their are no public discounts, we have always saved with AAA (I think our membership cost around $50/yr).
Deluxe resorts are 15% off in Value season, 10% in regular.
Values & Mods are 20% off in Value, 15% in regular.
Like the Prev. Poster said, check Mousesavers.com, it's usually up-to-date.
Look here, at Mousesavers, and Allears for public codes along with some great discounts at Swan/Dolphin. For public codes, you usually have to book at least 3-4 months in advance.
Buy an AP for AP rates. We stayed at the CR in March (peak season). Originally we had a public code rate of $237/night, but the AP rates were $199/night. It was worth it to get the AP to save more than $250 on our ressie.
If you book rack rate far in advance, go through Dreams Unlimited. They will apply the public code rates when they come out.