I've always liked BnB-- it's a great bike shop in Boston selling used bikes and teaching kids how to fix them.
They also send bicycles and bicycle parts to developing countries support organizations that build pedal-powered machinery for indigenous peoples including grain mills, concrete vibrators, and machines for pumping water and depulping coffee that use no electricity.
Their shop is located next to the Sam Adams brewery, so if you're in the Jamaica Plain neighborhood of Boston, consider stopping by.