The two biggest resorts that get discounted are WL/AKL, as has been mentioned. Right now I have an AP rate for AKL @ $139.00 per night. Last week I had WL for $139.00 per night and got free upgrade to Club Level.

The resorts that have very little to no discounts are Poly and GF. I can get discounts on CL but I have to book as soon as the rate comes out. Generally, as I'm getting within a week or two of my trip I will start to see space opening up as room-only's begin to cancel and/or you can see these at 44 days out when the package crowd starts to cancel/change their ressies. Always check for availability after (not at) 7am ET 44 days out or closer.
I went two weeks ago at the beginning of FD, unfortunately, but I was still able to change resorts due to late cancelations. So it is possible. You just have to be persistent.
Do what islandchick779 said and book as soon as possible. I get my hotel a year in advance and then apply codes as they are released. If no codes come out, then at least i'm PIF by the time my trip comes. I love putting my vacation on layaway. LOL