The only discounts that are currently available for May 2005 would be the
AAA discounts. You don't need to book thru AAA to get the discount, you just have to be a member. The discounts are in the 10% - 15% range.
I like
MouseSavers.com - WDW Resort Discounts for information on how to get the best rate on a package or room. If there's a deal out there, Mary knows about it and updates her website daily.
Most room-only discounts are not announced until a few months before they're good. You can check
MouseSavers.com - Historical Trends to see what kinds of discounts have been available in the past and when they were announced.
My advise would be to book the room that you want now and apply the discount code to it later. You can even book with a
travel agency that specializes in WDW, like
Dreams Unlimited Travel . They will monitor the discounts for you and make the calls to apply them to your reservation. The cost to you is nothing. It can save you the aggrevation of being "on hold" and paying for long distance calling. They'll even book your PSs for you! I was so pleased with how things worked out with my July trip that I used them again for a quick September trip.
Good luck with your planning!