This is a very short list of places where you can buy gifts that help someone else. There are many more. If you have a particular favorite, please feel free to post it here. Happy shopping!
Nothing But Nets: $10 of every hat & t-shirt purchase will send a mosquito net to Africa to help fight malaria.
UNICEF: Proceeds from sweet gifts like "My Little Monkey" support "child survival, protection, and development worldwide through education, advocacy, and fund raising." I'm a big fan of the I Never Forget a Face! Matching Game ($13.00).
DonorsChoose.org: This is like a grown-up, education-oriented version of MarkMakers. Teachers from underfunded public schools submit proposals for things they need (everything from a rug for a reading corner and wet erase markers to projectors and entire science labs). You can buy gift certificates for your friends, and they can choose which project(s) they want to fund. Proposals are searchable by total cost, the school's level of poverty, subject matter, and state. You may choose to fund all or part of a project.
Good Magazine: 100% of every subscription purchased goes to one of 12 organizations (like Room to Read, NRDC, and Teach for America)...you choose where your money goes.
Fair Trade goods: Fair Trade helps provide fair pay and regular work to artisans from around the world. Beyond that, buying Fair Trade is a great way to find unique, handcrafted gifts for your friends and family.
There are so many ways to find gifts that give back in personal, innovative ways. Check local arts organizations in your area. My friend Kate's modern dance collective Live Animals, for instance, just sent out an email to their subscribers offering a gift pack of homemade chocolate turtles (made lovingly by the grandmother of one of the dancers!) for a $25 donation. I will definitely be picking up a box or two of those for some chocolate lovers I know!