Exercise!

When my son was in public school, I was concerned and frustrated by the lack of physical activity the children received. With all the media attention given to childhood obesity in the United States, you would think schools (where the majority of children spend the greater part of the daylight hours) would be doing more to get children physically active. Yes, reading and math are important, but you aren't going to develop diabetes or heart disease if you don't do them for hours on end 5 days a week. Where as lack of physical activity does lead to major health problems that will follow you through the rest of your life.
Children also need to release energy. To have children (especially boys) sitting in desks for hours really isn't natural. However, elementary classes have gone from having physical education class every school day to only having p.e. 2-3 times each week. (It saves the school system from having to pay for multiple p.e. teachers.) In addition recess is given at the teachers' discretion. Teacher has to get paperwork done, students need to review material for an upcoming standardized test, then no outdoor recess.
Ok, now that I've had my rant. One thing I love about homeschooling is the amount of time we can spend outside, being active (or not)! We have science lessons outside, where the kids can really experience the things we've read about in books. We do social studies demonstrations. We spread out on the patio to do big, messy art projects. We can just sit outside and read. It is great!
In addition to playing, we also participate in sports. My oldest son plays soccer with the local soccer association. He plays in the spring and fall. My sister (who also homeschools her two children) takes her kids to an informal soccer clinic for homeschoolers once a week. My oldest son also takes karate classes. (J has been doing soccer and karate since he was 5. E is eagerly awaiting the time when he will be old enough to join "brubber.")