Here is the list of refurbishments/closings/openings directly from the WDW website:
To provide Walt Disney World® Guests with the highest-quality experience, attraction maintenance is occasionally necessary. Please refer to the following schedule to see what attractions may be closed during all or part of your next visit. For updated details, you may wish to call (407) WDW-MAGIC (939-6244), just prior to your visit. Dates of refurbishment are subject to change without notice.
Magic Kingdom® Park:
Mickey Mouse, Donald Duck and other popular Disney characters will appear in three-dimensional animation at "Mickey's PhilharMagic Orchestra," a new attraction scheduled to debut in 2003 in the Magic Kingdom Park. This attraction will replace Legend of the Lion King, which is now closed to help prepare for this new attraction.
Walt Disney's Carousel of Progress - Open seasonally
The Timekeeper - Open seasonally
Big Thunder Mountain will be closed for refurbishment August 24, 2003 - November 22, 2003.
The Swiss Family Treehouse will be closed for refurbishment
September 7, 2003 - October 24, 2003.
Epcot®:
No changes
Disney-MGM Studios:
Magic of Disney Animation will be closed for refurbishment
September 1, 2003 - October 31, 2003.
Rock 'N' Roller Coaster will be closed for refurbishment
September 6 - September 15.
The Twilight Zone Tower of Terror will be closed for refurbishment
September 22 - September 26.
Disney's Animal Kingdom® Theme Park:
Festival of the Lion King Theater will be closed for refurbishment
August 25 - September 19.
Downtown Disney® area:
No changes
Water Parks:
No changes