You can take an organized tour of the WL or the GF - each hotel offers a tour of its facilities. However, most people use the phrase to mean wandering around on their own.
In general, I enjoy taking a trip to the monorail hotels (Poly, GF, and CR) by riding the resort monorail loop. There are some great restuarants and famous Disney theming - it's a nice break during a hot afternoon at the MK.
The WL and AKL have amazing, amazing theming. The lobbies are stunning and the grounds are worth a look at both. Again great restaurants, and, of course, viewing locations for the savannah at AKL. It's an easy hop from the themeparks to visit either.
The Epcot resorts also have some nice restaurants, and it's easy to take a look around as you go from Epcot to MGM. The Boardwalk has some fun activities, too. I also think the Port Orleans resorts are fun and worth a look. They're an easy boat ride from DTD, so they're easy to fit in the schedule.