Yes, you're patting yourself on the back for doing shopping and helping people. But how much did you really help? Here's how to judge.
The Buy-One-Give-One model of companies such as TOMS Shoes has been in the news a lot lately - Check out some further arguments for and criticisms against it via:
Stanford Social Innovation Review: http://www.ssireview.org/articles/entry/inside_the_buy_one_give_one_model
Dare to Innovate: http://www.osezinnover.com/free-fish/