I don't think they are listed on the maps, but there are many, many little out of the way places where you can take a break.
I'll start with one example in each park...
MK- The lower tier of Tomorrowland Terrace is usually pretty empty most parts of the day. It is shaded and still offers a nice view of the Castle.
Epcot- too many to list, but I particularly like near the back of the Japan Pavilion. There are benches and shade.
DHS- a little tougher to find spots that are always quiet- but in the less busy seasons, there are plenty of places to find. In front of the Brown Derby, there's a nice tree-lined pathway with benches. But when the Disney Channel street show is running, it's not all that quiet. But I did meet a dad over there this week with a sleepy baby- so it is enough away from the LOUD show to still be comfortable.
AK- if it's not lunch or dinner time, the lower dining levels out behind Flame Tree BBQ or some of the rooms in Pizzarfari are nice, shaded and usually quiet spots.
I'm sure others will post their favorite quiet spots too.