(Don't forget to read our disclaimer and do some double-checking of your own!)
Boston College
Catholic University, Washington, DC
East Tennessee State University (summer programs) - http://www.etsu.edu/cass/albaeire/ - Appalachian, Scottish & Irish studies
Fairfield University (CT) - http://www.fairfield.edu/cas/irish_index.html
Harvard
King's College (PA)
Loyola Marymount University, Los Angeles
Loyola University, Chicago
Southern Illinois University at Carbondale
Stonehill College, MA
Trinity University, Dublin
U Mass Boston, Stonehill, MA
University College Cork (Cork, Ireland)
University College, Dublin - http://www.ucd.ie/icsifl/
University of Aberdeen (Scotland)
University of Arizona
University of Missouri at St. Louis
University of St. Michael's College in the University of Toronto - http://www.utoronto.ca/stmikes/celticstudies/
University of St. Francis Xavier (Antigonish, Nova Scotia) - http://www.stfx.ca/academic/celtic-studies/index.html
University of Wisconsin-Milwaukee - their center for Celtic Studies keeps its own list of programs - http://www.uwm.edu/Dept/celtic/links/programs.html