First of all, you'll probably want to work these days off into the middle of your stay, rather than just at the end. Some suggestions:
Character meals at Chef Mickeys (Contemporary Resort), 1900 Park Faire (Grand Floridian), Cape May Cafe (Beach Club), Olivias (Key West), Ohana (Polynesian), as well as restaurants in the Swan and Dolphin. For more info:
http://wdwig.com/cb.htm
Miniature golf at Fantasia Gardens (near Swan and Dolphin) or at Winter/Summerland (near Blizzard Beach)
Free boat rides: Around the monorail resorts and Wilderness Lodge; Around Boardwalk, MGM, Epcot, Swan & Dolphin and Yacht and Beach Clubs
Boat rentals: many resorts
Strolling the Boardwalk, etc. in the evening.
Downtown Disney Legoland.
Electric Water Pageant at the monorail resorts and Wilderness Lodge (free!)
Savannah viewing areas at Animal Kingdom Lodge (free!)
Storytelling at Animal Kingdom Lodge (free!)
Resort tours at Animal Kingdom Lodge or Wilderness Lodge (free!)
Magic Kingdom fireworks from outside the park---from California Grill (Contemporary Resort), from observation deck outside CA Grill (free!), from Polynesian Beach, from a well-timed boat ride, etc.