GISCorps is a group of GIS professionals that volunteer their time and skills in order to create a better world. Started in 2003, GISCorps' goals revolve around helping to improve quality of life through supporting humanitarian relief, enhancing environmental analysis, encouraging and fostering economic development, supporting community planning and development, strengthening local capacity by adopting and using information technology, and supporting health and education related activities.
To date, GISCorps has launched almost 200 missions globally aimed at giving back. Not surprisingly, they have an array of interactive maps that showcase their projects and locations.
For more information on GISCorps and the work they're doing throughout the world, check out their website.