Scuba diving (though I've hardly done that this season! Friggin school!). Reading. SF, fantasy has largely lost it's interest for. There's so little creativity in that genre :-(. My most recent 'discovery'is China Mieville with Perdido Street Station. Other favourite authors include Greg Bear, Isaac Asimov (though not the Foundation books), Tad Williams (Otherland is amazing (and a loooooooooooooooooooooong read)) etc, etc. I keep wanting to get into last turn of the century horror/mystery/gothic books, however I hardly have time (make time?) to read anything other than stuff I need to read for my studies.
I'm planning on joining a horseriding club in September.
@wayne:
Oh about flying your own aircraft: I'd suggest you take another look at ULV/MLA aircraft :-).