Ralph Lee Smith has his second edition of Appalachian Dulcimer Traditions out now which is a good resource on the history of the dulcimer and good information on some of the early builders. His website is http://www.ralphleesmith.com/Books___CDs.html.
Kevin Messenger, John Knopf, and Dan Cox, all members here make dulcimers in the pre revival style and know a good bit about some of the early builders. There are many builders of modern instruments all across America and some in Europe as well.
Over on www.everythingdulcimer.com, David Bennet has been publishing a wonderful nearly daily series called Today In Mountain Dulcimer History. You'll find info about Amburgey there, I know...
For a "history lesson" on builders, find a copy of Jean Ritchie's book The Dulcimer Book; also Michael Murphys The Appalachian Dulcimer. Both books are out of print, but can be found, and both have lists of dulcimer builders that go back into the 1960s.
Are you looking to have a dulcimer built? Trying to find more information about a specific luthier? If you have questions we can probably help.
We don't host a comprehensive list of dulcimer makers here on FOTMD. However, over on Everythingdulcimer's site there are a couple of things that might help you:
http://everythingdulcimer.com/builders_display.php
http://everythingdulcimer.com/discuss/viewtopic.php?t=23533
