If you register with the shopping site GoodShop, your society can earn money when people select it from a list of charities and schools, then shop on participating Web sites (including eBay, PetSmart, Target, J. Crew and more). The retailer then donates a designated portion of the purchase (averaging about 3 percent) to your group.
How do you add your society to the potential beneficiaries? If the group is a registered nonprofit, you can submit it for participation. The approval process takes a couple of days.
GoodShop has a search engine called GoodSearch that works similarly: A Web surfer selects a charity and then does a search (powered by Yahoo!), and the charity gets a small donation from advertisers on GoodSearch.
I counted at least 15 genealogical societies already on the GoodShop/GoodSearch list. See if your society is one of them here.