I'm not going to mark National Thrift Shop Day by suggesting that everybody out there should go and buy something at a thrift shop (although you know that's one of my favourite things to do).
I'm not even going to mark it by suggesting that everybody should donate something today (although you know how much fun I have unpacking books at the MCC store. It's Christmas every week).
I'm going to suggest something far more radical.
Non-profit thrift shops...in spite of all the good they do by raising money for the ministries and charities that run them and by giving lots of stuff a potential second life...reflect something about our world, our culture, our attitude towards buying and un-buying stuff, that isn't a good thing. In a perfect world, ministries that run thrift stores would have to find another way to raise money, because people would be buying just what they need, using things longer, fixing what's broken, trading what's outgrown, borrowing what they can, re-purposing things themselves. And those organizations wouldn't totally mind that, I think, because any one of them accepting donations of Stuff must deal with an Increasingly Big Headache of Responsible Disposal.
So keep the thrift store of your favourite charity in mind today by not buying one particular new thing (besides food or other consumables). That way, when that one unbought thing doesn't arrive at the hypothetical end of its usefulness to you, you won't have to drive it to the thrift store. Nobody will have to unpack it; nobody will have to price it and hang it on a rack; nobody will have to pay the cost of the computerized cash register system and the credit card fees; or (if it sits unsold) nobody will have to bale it up and figure out where to send it next. By not buying something new today, you've created one less future thing-in-thing-out decision for a crew of staff and volunteers. Wasn't that easy?
(But you could also send the charity a financial contribution.)