First and foremost: travelling. I'm a bit of a globetrotter and my mission is seeing as much of the world as I can in this lifetime.
Other less expensive hobbies include: reading (classics, historical (and other) novels, African literature ...), wine tasting (and drinking, of course!), photography, music (classical, folk, African, Brazilian, rock...), cycling, cinema.
I used to love studying/learning but I just don't seem have the same energy and concentration capacity as I used to. Getting old perhaps?