Check out this post on TechSoup, called Add Charity Shopping to Your Web Site which details how to add a charity shopping mall to your website. If someone ends up buying something through your shopping mall, you get a small percentage of the profits. For some motivation, TechSoup provides some numbers from a case study:
It’s possible to make good money using a charity mall. The Larkin Street Youth Center in San Francisco made $1000 worth of profits in a few months with iGive.com, according to the SF Gate article A New Way to Give .
It doesn’t sound easy, but if you are driving enough traffic to your website, it sounds like something that could take off without that much work.