I do a little writing (for myself) and I'm rarely w/o a book. Other than that, I don't do much. I don't have talent for singing, dancing or playing an instrument and I don't have the patience for arts and crafts.
Wow. I'm not that exciting.....
Actually, I've discovered that most of the things I could really get into are just not going to happen. It's either too expensive (horseback riding) or I'm not in the right setting (snowmobiling--I love it, but there's not enough snow in Pasadena, CA )
I guess I'd have to say in terms of raw output, my most common hobby is writing. Compulsive writing. I also build models and paint figures, and the writing compulsion and model-building compulsion comes together on my modeling blog, kit-reviews.blogspot.com. I'm also an amateur (and amateurish) historian with a special weakness for Ancient Rome, the Cold War, and earthmoving equipment.
There's more, but I'm trying to teach myself to be concise.