This is why I recently took up birding as a hobby. It allows me to do several things I enjoy -- walk; ride my bike; enjoy nature; compile lists; take, crop and organize photos; spend time in my yard. In just a few short weeks I've honed my visual and audio observatory skills, learned a great deal about various birds and their habits, and gotten exercise without even trying. And it's completely unscheduled.

Most of my other hobbies -- including anything that involves writing -- too easily become "work." This one is there for me whenever I like, or sometimes an interesting bird will cross my path when I'm doing something else. (I now carry binoculars in my purse, so I can take advantage of the opportunity.)