'There's walking, doing summat to help people, going to museums, reading/libraries, board games, people watching...'
And in the spirit of this advice, here are some things to try:-
Grab an ordinance survey map from your local garage or newsagent, get a big stick and go on a hike. If you get bored, you can always pretend to be Gandalf and use the big stick to ward off a Balrog.
Volunteer for a charity. This being a blog about mental wellbeing, let me point you in the direction of SANE but you could also volunteer as a steward at a music festival for Oxfam or get on a plane and go and work with elephants. Why not eh?
Go to a museum you've never been to before. If it's got dinosaur skeletons, even better. If you have kids, get them to make some dinosaur skeletons our of Playdoh and set up their own museum. I used to do this as a kid on rainy days. Hours of fun. Entrance fee was 20p.
Books never go out of style. Turn off your Kindle (grr) and dig out your favourite book and curl up with it for a while.
Get some friends together and have a board game night. My favourite board game at the moment is Dixit.
And people watching never gets old. Just don't, like, stare. I people-watch on the Tube, and give the other passengers prizes in my head. Prize for the best hair, prize for the biggest fashion mistake, prize for person who looks like a character from any science fiction film...you get the idea.