Music (listening to, playing, and occasionally trying to write some)
Gaming (computer and pencil & paper RPGs w/ friends; mostly I try to find a way to play games without having to interact with other people)
Gardening (mostly trimming and hacking things back)
Birdwatching
Reading (usually WWII, other history, or fantasy fiction)
Starting things that I never finish
Camping
Enjoying the food I eat (*pats stomach* Can't you tell?)
Playing with my dog
Daydreaming (usually about an end result with no idea how to get there)
Staying up later than I should
There's probably more I could add, but see the last hobby mentioned....
EDIT: I also have a strange habit (hobby?) of collecting books on subjects that I never quite use. Roleplaying game books, falconry books, martial arts books, violin books. I always intend to pursue a subject, but seem to lack the perseverance to actually pursue it.