UPDATE: This link is no longer functional. We're leaving up this post as a record of the project, and so people can still view the comments.
If you shop on Amazon in the countries listed below, you can earn a substantial commission for charity by doing so via the links below. This is a cost-free way to do a lot of good, so I'd encourage you to do so! You can bookmark one of the direct links to Amazon below and then use that bookmark every time you shop.
The commission will be around 5%, though it varies by product category. This is substantially better than the AmazonSmile scheme available in the US, which only gives 0.5% of the money you spend to charity. Amazon's 'Associates Program' pays this commission for referring purchasers to them, from the unaltered purchase price (details here). The money goes to Amazon accounts that I've set up for this project, and from there I'll always direct it only to GiveWell-recommended charities. For ease of administration and to get tax-deductibility, I'll send it to the Schistosomiasis Control Initiative until further notice, though if you make a large purchase which yields over £50 of commission you can ask me to donate it to another charity.
Direct links to Amazon for your bookmarks
If you'd like to shop for charity, bookmark the appropriate link below now:
I'll add other links here and on the main 'Shop for Charity' page later, including for France. I'd love to hear suggestions for good commission schemes in other countries. If you'd like to share these links with friends and family, please point them to this page or even better this project's main page, as this is the safest way to ensure that the commission gets earned.
Happy shopping!
'Shop for Charity' is a Charity Science project

Thanks for these helpful comments. Taking them in turn:
I'd added effective-altruism.com as one of the domains which could send links, and it got accepted (though people going via the main 'Shop for charity' page on my website as you suggest is not a bad idea.) I think including the links in this post will increase the chance that people'll actually bookmark them, and Amazon do seem to let bookmarks work (e.g. those from the sidebar of http://slatestarcodex.com/ ).
Yes, people can indeed rest assured that this money'll never benefit me :) Hopefully the edit I made in response to Ryan and Topher's suggestion makes the process transparent: "The 5% comes from Amazon's 'affiliate' scheme, and goes to affiliate accounts which I've set up for this project, the money from which I'll always direct only to GiveWell-recommended charities. "
This extension appears to be http://bit.ly/1ruTdZA