Why am I making this post?
While the content discussed below is relatively low impact compared to many of the ideas discussed on this forum, it requires so little time/money that the impact per cost still looks encouraging.
Using smile.amazon.com means that amazon will donate 0.5% of your purchases to a charity of your choice. The AMF and Animal Equality (givewell and ACE top charities respectively). This is free money, not very much, but for most people who use amazon, enough to be worth the ~30s it takes to set up.
Amazon smile lets you start conversations about charitable effectiveness with people who otherwise wouldn't go anywehere near EA topics. A social media post, with, for example, why you've chosen AMF for your smile donation, and why you think it's important to choose carefully rather than go with one of the defaults, is a gentle way in to thinking about idea of charitable effectiveness, and anecdotally has led to positive conversations with people I think a harder sell would have put off.
Why might this be a bad idea?
If amazon smile causes you to spend more than you otherwise would have, especially on things you don't need, you could do much more good by donating directly instead of spending on Amazon. This is, of course, less of a problem if you wouldn't have donated the extra money you are incentivised to waste on Amazon.
Signing up for smile may cause people to feel like they've "done their bit", and reduce donations elsewhere. This seems somewhat unlikely for EAs, although not impossible. It seems somewhat more likely for non-EAs, though given that charitable effectiveness can vary by several orders of magnitude, if non-EAs are persuaded by you to send their smile donations to an effective charity this may not be enough to make the overall effect negative.
Even if the effect is positive, surely it's too small to be worth doing anything about?
It depends how likely you think I am to be right about this being a good way of starting conversations about charitable effectiveness. If you think I might be right, but don't want to waste time writing your own long-shot post to share on social media, feel free to use mine. It was written for my particular social media bubble, yours may be different, but at the very least it may save you some time.
I'm not saying use Amazon, but over Black Friday, Christmas, and being too lazy to go outside, you're probably going to. If you do, you may as well use https://smile.amazon.co.uk and do some good at the same time.
Depending on which charity you choose to give to, the amount of good you end up doing could be surprisingly large. My top picks are below:
Against Malaria Foundation - https://www.againstmalaria.com
Read more about their effectiveness here: https://www.givewell.org/charities/amf#Costperlifesaved
Animal Equality - https://animalequality.org/
Read more about their effectiveness here: https://animalcharityevaluators.org/charity-review/animal-equality/