Besides frequenting this site and others online I sometimes read, watch a movie, listen to music, play computer games, play my guitar, read RPG books and fantasize about the campaigns I'll never run, and also watch the occasional bird.
I'm really terrible with that last one. Any time I see something flying by out of the corner of my eye, it gets my full attention immediately. Most of the time it's just a sparrow, pigeon, goose, or crow, but every now and then it'll be something special.