I've just bought the (download only) "English songs and ballads for the Appapachian Dulcimer" by Lance Frodsham for MelBay.com.
I commend it highly - their tech. support staff were immensely patient as I wrestled with the (quite complex) downloading arrangements (highly rights-protected - but reflected in a fair price) over several days.
Secondly the guy who put it together is of my vintage and the song choice is cracking if your hinterland is "trad. arr. Shirley Collins/Copper family; Waterson /Carthy; Fairport, Steeleye". For me the price was worth it for tab of Claudy Banks" in DAdd!