For AK: Kali can be REALLLY FUN if its REALLY HOT and you want to get wet. If you don't, DON'T even try it. You will get soaked. You can't go to AK without doing Everest, Safari, Dinosaur, and a lot of people love Festival of the Lion King. They had a bird show that was pretty neat, those things were ENORMOUS, so that's neat if you like unsual birds and they have it and you have time. Right now, those are the highlights and you can take or leave anything else AK has (and I have no opinion about their river fireworks, haven't seen it but its probably good, they usually are?)
For MK: Agree on all the kiddy spinny stuff. Teacups, Dumbo etc. Don't forget Bear Jamboree, we only went in because there was nothing else to do and it let us sit down for a while. Anyone got a clue what the bear that sings about the blood every where and blood on the ground is talking about....

For us, no MK is complete without Buzz Lightyear, Space Mountain, Belle (well, thats more for me) Ariel if there isn't a wait, Monsters Laughfloor (this is a MUST), Philharmagic (getting a face lift maybe?). The rest are just if we have time: Pirates (I hear CA's is better), Tiki Room (if you want to sit down, although I enjoy it when it comes on pandora, old memories I guess), Jungle Cruise (how can it still be there? we usually skip), Presidents, Thunder Mountain if the wait isn't worse than 30-40 min, Splash Mountain if the wait is like nothing. I'd put Small World at a higher priority (but you have that anyway) just because they have great outfits and I like the dancers. Peter Pan was a big let down last time (not like I remember?) so I haven't bothered in a while. I think CA's is better there too.
DEFINITELY DOOOO NOOOTT agree on skipping Nemo and Turtle Talk. Those are MUSTS! Especially if you are new to the World (vs the Land). You might already know Turtle Talk, but I love Nemo because the end is very special to me and I think its really neat. The Living Seas or whatever they want to call it now is always a must for us just like the Land with Soarin (of course you have that), Test Track, Mission Space (bonus for the fun games if you can get enough people, we couldn't this last time

) and of course Spaceship Earth.
Maelstrom, the Mexican boat, or any of the World Showcase "attractions" can be passed up if you are on a time budget. We love the World, but we don't always do the attractions. Very low priority to us unless you are dying to try something. On the other hand, we always try to make time for one of the Chinese Dragon Acrobatic Shows, as they are always amazing.
HS, agree on Backlot unless you have all day and have ridden everything you want as much as you want. DO NOT, and I mean this in all seriousness, DO NOT GO INTO THE PIRATES EXPERIENCE!!!! That is the worst thing ever offered as an 'attraction' on a map. It would be better if they locked the door and pretended it was a closet. We saw Lights Motor Action once, and it was neat, but its not on my absolutely must dos. And it was HOT and I got eaten alive in the stadium at 1pm in the afternoon... Muppets 3D used to be really funny but I don't like the new one with the imagination cartoon nearly as much. Still, we like muppets so we always go to it (But I think you might have it too in CA.) Of course, TSMM is a BIIIGGGGG DEAL at WDW, but not as big a wait in CA I hear (which is why I'm comin!). Indiana Jones show we have also skipped for years for sake of time. I WISH WISH WISH I had time for Americal Idol but its SUCH a time sucker, I've never gotten to do it, with all the rehearsal and prep time. We never do the Disney Junior shows or anything like that either cuz we don't have kids. I still love Voyage of Lil Mermaid and always go at least once. I like the theater, I like the real actors and singers and its relaxing. We also have to draw at least one character, and this time, we got Stitch! Woohoo! He was fun. Of course, Tower and RnRc are musts for HS, but if those few were all I got to do before hopping, I'd be happy with that. I always do like the movie sequence at the end of Great Movie ride, just something super nostalgic about it. Soundstage is funny if you haven't done it before and have some time too.
I guess that's it for now. I'd be curious for yours at CA since we are heading out there tentatively next fall.