I've also started running a lot and climbing. They're pretty fun ways of keeping fit.
maths and science-y stuff (at least I should be after the amount of time I spent studying it)
breaking stuff to find out how it works then attempting to fix it again (but only stuff I own)
Movies: Sherlock Holmes, Marvel films, Star Trek, Lord of the Rings.
TV shows: Community, Big Bang Theory, Game of Thrones.
access to good books (see also the internet)