On one of our non-park days we sleep in, boat over to Fort Wilderness and futz around over there (eat breakfast at Trail's End, walk the nature trail, hang out at the petting zoo) and then spend the afternoon/evening at DTD.
On the other non-park day (we usually take 10-12 day trips, so we need some R&R time) we sleep in, play at the pool, have a nice meal at the resort, and at some point do DH's favorite thing to do at WDW--rent watermice. We usually try to do some resort hopping, too.