Sleep in.
Go out for brunch with the wife.
Some afternoon chores around the house.
Some kind of variable evening plan--dinner with friends this sunday, movie last sunday, pretty variable.
Kick back and relax in the evening.
It's basically a day of rest, the household chores I do are almost part of the relaxation, straight forward low pressure low stress stuff unlike my work.
Really the big deal for me is that I can sleep in. In my job I deal with people on multiple continents so in the regular work week I get fucked over by timezones and often find myself dealing with crap at really fucking odd hours. Try finding a time for a meeting with people in Europe, Asia, and North America--it fucking sucks.