Favorite Things to Do on a Day Off When the Kids Are in School

I have some vacation days that have accumulated throughout the year that I now need to use up in December and January, so I'm doing something new (because I have to). I'm not taking them all in one big chunk - I'm spreading some out on Mondays and a Thursday during December. Today was one of those days and I was reflecting on a couple of things I like to do on a day off while the kids are at school:

1. Do stuff with Kim - it's fun to be able to run errands together, go to the grocery store, do projects around the house, etc. Kids often don't allow us to just do simple "us" stuff that we used to do before we got outnumbered by rugrats.
   
2. Manual Labor Projects - I love to get out and do projects. Because I work in an office most of the time and work with people - I love to get away from both (no offense people) and do projects that are a physical challenge and have a clear completion goal. It is sometimes hard to see objective results when dealing with people because most relational situations stay in a permanent state of development. So on days off I love to start something and finish something and see the result. Often #1 and #2 happen together because Kim builds houses and often wants me to help her with her latest house project.
3. Head to the gym - I always try to hit the gym on a free day and pick up a raquetball game or a run. I typically catch up on some podcasts that have been backlogging or blast music into my skull and sweat like crazy.

What are some of your favorite "free day" activities?