eScrip. This service partners with merchants who give back a percentage of purchases you make to the organizations you care about. Purchases are tracked through registered cards (store loyalty, credit/debit). To set up donations via eScrip, go to https://secure.escrip.com/signup/index.jsp, set up a free account and select Sustainable San Mateo County as the organization you wish to support.
Then register the credit card(s) that you usually use for checkout, or your merchant Community Card. For some merchants, you only need to register your email and phone numbers. Once you have an account, you can click on “Where to Earn” to see stores that honor the eScrip program and sign up for the ones you patronize.