I wanted to add say that I found the lists by Lindahl very helpful for pre-18th century ballads in the Child Collection, and also the article by Dani Zweig on "Early Child Ballads". Here is Lindahl's information as posted above by Mick Pearce:

http://www.pbm.com/~lindahl/ballads/child.html

As well as Lindahl's "Sixteenth Century Ballads: A work in progress" :

http://www.pbm.com/~lindahl/ballads/

And here is the article by Dani Zweig, with some very helpful information about Child ballads in the 18th century:

http://www.pbm.com/~lindahl/ballads/early_child/#partii