There are a number of excellent string classes taking place at the Milwaukee Irish Fest Summer School this year (August 11 - 15, 2014):
John Carty: intermediate and advanced level fiddle classes
John Doyle: guitar and English language ballad singing classes
Eamon O’Leary: bouzouki
Fergal Scahill: fiddle improvisation and variation class
Alasdair Fraser: Scottish fiddle workshop (Friday morning only)
David Howley: Guitar workshop (Friday morning only)
And for beginners:
Intro to Irish fiddle with Ed Paloucek
Full information and registration info on the website: http://irishfest.com/Summer-School.htm