MK: Pirates of the Carribean, Haunted Mansion, It's a Small World, Space Mountain, Buzz Lightyear, Mickey's Philarmagic
Epcot: Innoventions, Journey into your imagination, Honey, I Shrunk the Audience, The American Adventure
MGM: Muppetvision:3-D, Rockin Rollercoaster, Star Tours, The Great Movie Ride, One Man's Dream
AK: Dinosaur....other than that there really is no escape from the rain or heat.
Also if it starts raining or gets really hot, this would be the best time to take a break and get something to eat. There are so many restaurants around the parks that it is nice to just sit down for a while and watch everyone else run through the rain. Ponchos are a great thing to have with you at all times. This way you can still enjoy some of the rides while everyone else is running for shelter. Sometimes the rains don't last that long so it might be the time you finish a meal or by the time you have waited and got on a ride. Either way there is always something to do in almost any weather.