Rebann,
I remember looking into this myself a few years ago and it is slim pickins. I would be tempted to ask why you want this if this is your first trip to WDW. Our first four trips to WDW we were at parks non-stop. The first trip we took one afternoon off to go swimming and then a couple "late night dips" I guess I'd be tempted to ask when you're going (what month) - ages of children - and budget. We have stayed at quite a few hotels both on site and off (and I've researched alot) and I'm usually a pool fanatic wherever we go. While there are no indoor pools on site, every resort has heated pools. When it's colder out, they heat them more! Some of the hotel offsite do not heat their pools. You may also want to check the pool hours. For most resorts on site the pools are open very long hours and sometimes 24 hours. If you're staying offsite with an indoor pool that's only open until 9 P.M. you may not get much use out of it.
I am also increasingly disappointed in the indoor pools of new motels. We've stayed in some that the pool is so small if you get more than 10 people in it, it's crowded.