You could say that it is everywhere and nowhere. There are many Quaker organizations with different functions and which relate to different parts of the larger Quaker movement. A few of the better known examples in the United States include: American Friends Service Committee (which puts Quaker values into action by operating service, development, and peace programs throughout the world), Friends Committee on National Legislation (which lobbies on behalf of Quaker values), Friends Council on Education (which works in support of Friends schools), and a great many others, including schools and colleges, peace and justice programs, retreat centers, services for the aging, and more. In Canada, the Canadian Friends Service Committee addresses the peace and social concerns of Friends. Each of these organizations is independent of the others, but there is much collaboration and interconnection.
Friends World Committee for Consultation is a worldwide organization, headquartered in London, that promotes fellowship among the various branches of Quakers, but it does not speak on behalf of all Quakers or have authority over them. Some of the Quaker branches have their own “umbrella organizations,” including Friends General Conference (that's us), Friends United Meeting, and Evangelical Friends Church International.
Quaker congregations are affiliated in larger regional bodies called yearly meetings. There are 34 yearly meetings in the United States and Canada.