Whee, lucky you! I love WDW!! I'm going to repeat a few things that others have already said (Tiff had a lot of good comments), but here are some things I like:
Magic Kingdom:
SPLASH MOUNTAIN! Probably my favorite ride at all the parks.
Mickey's Philharmagic - the newest 3-D movie. The champagne corks popping at you at the end of "Be Our Guest" is now my favorite effect out of all the 3-D shows.
I will second the advice to SKIP Stitch. I love Lilo & Stitch, and they deserve a good attraction, but this is NOT it.
EPCOT:
Mission Space is awesome! You do pull G's. Don't go if you're claustrophobic or prone to motion sickness.
"Soarin'" wasn't open yet when I was there in Dec. '04, but I would like to try that.
Tiff is right about exploring World Showcase.
Disney/MGM Studios:
Tower of Terror!! Woohoo!! I am a big thrill ride WIMP but I love this. It's like having a big tank of adrenalin pumped into a major artery. I have not yet worked up nerve for Rock 'n' Roller Coaster but am determined to do it next time.
Animal Kingdom:
It's Tough to Be a Bug - Not only is the show fun, the lobby is full of bug-themed Broadway posters (like "My Fair Ladybug" and "Web Side Story") and they play showtunes as if buzzed/chirped/etc. by bugs.
Maharaja Jungle Trek - A walking tour featuring big, gorgeous tigers - very cool!
DO NOT go on Kali River Rapids unless you want to spend the rest of the day as a dripping sopping thoroughly soaked and drenched pile of water.
Food:
If you're game to hang out with Pooh and Tigger, the Crystal Palace at the MK has a good breakfast buffet; plan your seating as early as possible, and you can eat before the attractions open and be ready to go when they do.
Kona Cafe at the Polynesian Resort (a quick monorail ride from the MK) was a great place for a nice relaxing lunch last time I was there. They've changed the menu somewhat since then, but I'm sure it's still good.
I love Marrakesh, the Moroccan restaurant at EPCOT. If you live in a major urban area with lots of diverse ethnic restaurants, it might be no big deal, but for me, it was an adventure. The Royal Feast is great, with bastilla, lamb, chicken, couscous, and crepes for dessert. Try the iced mint tea.
Man, now I really want to go!
"In my own little corner..."