Learning to play an instrument
Learning a new language
Learning any indoor skills like cooking, home repair, computer skills or other
Reading more often or across genres
Staying in better touch with people
These are all things that I thought I would do if I had more time. It turns out that time was not the issue. It was an issue of motivation. Maybe if I had some end point in mind and the goals were stepping stones, the motivation would have come easier.
For example, we are planning a trip to South America, I would be more motivated to learn some Spanish.
I also clarified that I really enjoy my professional life and that I enjoy health and fitness. I made efforts to eat better and organized my home and days around exercise. I watched a lot of health and fitness related television.
I also enjoy being organized and made several passes organizing my clothes, books, digital media, etc. In another life, maybe I could have made a good librarian.
Another surprise was that I spent near zero time following financial markets. Investing and personal finance were really enjoyable activities for me for over 20 years and when I stepped away, I completely stepped away.