Do these rides usually have short lines??
How about Monster Inc Laughing Floor at MK and Turtle Talk at Epcot?? Are these good options??
Any A/C places at HS???
The show-style attractions often have a waiting room before the theater, and there may or may not be a line before the waiting room. Depending on when you arrive, you may spend the full length of a show in the waiting room even if there is not a line, and in many cases the waiting room will not have a place to sit.
MK:
Mickey's Philharmagic - queue and waiting room are indoors but have no seats
Hall of Presidents - don't remember if there are seats in the waiting area
Carousel of Progress - line forms outside, but I've never had to wait longer than it takes for the next section to roll to the loading position
Country Bear Jamboree - waiting area has a few seats
Laugh Floor - yes, it's a good option, though the lines may get longer than for some of the older, less popular shows
Epcot:
Ellen's Energy Adventure - this ride has
massive capacity and I have never seen a set of its ride vehicles completely fill. There's a pre-show, but it's air conditioned and there are a few benches.
Turtle Talk - another good option, though there may be a longer line. No seating in line, but the line is at least indoors.
I've personally never had to wait more than the length of show to get into a World Showcase film, but your mileage may vary. I don't remember if the film in France has an indoor waiting area, but America's waiting area is indoors, air conditioned, and has benches. I think you can probably even just go in there and sit without seeing the show if you don't care to commit to it; it's also where the Voices of Liberty sometimes perform.
In general you can just sort of hang out in most of the pavilions in Future World.
AK:
I haven't been to Finding Nemo or Festival of the Lion King recently and don't recall how the queues are set up. I think they might have set times you can look up on the schedule?
It's Tough to be a Bug - the lines can seriously vary. I've seen it sit at a five minute wait all day some days, and be quite a long wait other days.
HS:
One of my favorite spots to rest in HS is Writer's Stop, which is at the end of Streets of America nearer the entrance to the park. It's a relatively quiet little coffee shop/bookstore, and while it has very limited seating, most people don't seem to know it's there. If you're in that part of the park it's worth checking to see if there's an open table in the back before resigning yourself to hanging out in one of the bigger CS restaurants.
Muppet*Vision doesn't have seating in its waiting area, but I've never had to wait for more than the length of the show.
Great Movie Ride is another one that varies, as gatorlisa said, but once you're on I think it's something like fifteen or twenty minutes of sitting.
Another spot at HS is the Commissary (ABC Commissary? Don't remember the name). It's a CS restaurant kind of to the left of the Great Movie Ride (describing location in HS is difficult, sorry). I was never particularly impressed with the food, but there's ample indoor seating and you can always just get a soda to nurse in there for a while. Same kind of deal with Pizza Planet