You can learn a lot about someone by their hobbies. My dad's hobbies, for example, are completely different on work days than non-work days. On non-work days, he will sit in his chair and read, or he will simply watch TV. On work days, however, he will drive as far as humanly possible to eat somewhere and normally spend 2-3 hours between driving and eating.
My main hobby is reading, but lately, I've renewed my interest in PC Gaming. My interest in going to the gym is coming back too... but that is something I'll have to make myself do :p