cookery book I wrote years ago for medical charity Action for ME. I wrote to the charity asking if they'd promote them (hadn't promoted it for years, as there is a newer version that needs to be sold) and lo and behold, I sold 8 in 24 hours just via Paypal and the charity website! Now have 11 sales (much frantic packaging and spreadsheeting) and 6 more yeses, so have sold all but one, which I shall keep 'just in case' (of what I do not know - may declutter later!). So the charity will make some money and I have some space.
As Action for ME has also given a link to a newer version of the cookbook, that is also selling. So both charity and publisher are now happy, and as I take 25% of royalties from that (though sometimes I don't bother) I am making a tiny bit of money too.
It's amazing how different things are now than when I first brought the book out, in 2004. Now, you can instantly publicise something to thousands of people who can also instantly buy it. In 2004 people did not use websites, Paypal or Facebook like this and I was knee-deep in cheques for weeks.
Anyway, it just shows how a bit of decluttering leads to unexpected benefits, to oneself and to people you don't even know.