Sundlun was a delegate to Democratic National Convention in 1964, 1968, 1980, 1988, and 2000, as well as to the Rhode Island Constitutional Convention of 1985. He was a member of the Providence School Board from 1984 to 1990. And from 1995 until his death, Sundlun had been teaching political science and Rhode Island history at the University of Rhode Island as "Governor in Residence".