I’ve been using Give As You Live since just before Christmas and think it’s a really great idea. It doesn’t cost you anything, you download the browser plugin and it then notifies you when you’re shopping with an online retailer that will give a % of the sale to your chosen charity.
The vast majority of online retailers do contribute to charity through the app, however they all give varying percentages, for example see this search for “photobooks” on Google:
Kinda helps you decide who to shop with if they are all offering a similar product!
I’m supporting Macmillan Cancer Support through the app — why don’t you support your chosen charity – it’s free and easy.