[2] Harrington was a board member of the Eugene and Agnes E. Meyer Foundation,[3] Consumer Health Foundation,[4] Bowie State Board of Visitors[5] and co-lead of the Robert Wood Johnson Place Matters special committee.

[9] He worked as a senior fellow and faculty member at the James MacGregor Burns Academy of Leadership at the University of Maryland.

[9] Harrington was appointed to the State Senate in 2008 to fill the vacancy created by the death of Gwendolyn T.

His oldest son, Stephen, is an alumnus of Morehouse College and the Brown University Graduate School.

David's younger son Christopher is an alumnus of Dickinson College and has an MBA from the Smith School at the University of Maryland.