I lived in the Netherlands for nearly seven years, and the only Dutch traditional songs I found were translated English shanties. But...

a) In a very roundabout way I came by a song, "Ik zeg adieu" (I say adieu) published in 1645 in the "Antwarpse Lied Boek" (Antwerp Song Book). A wonderful, sweet parting song supposedly sung by a mail order bride on her way to Java as she parts from her mother, in those days presumably forever. It's in Flemish/old Dutch, unsurprisingly as in those days Antwerp was part of the Lowlands ethnically. Seek it out (there are MP3s of various versions on the net), or get me to sing it to you some time.

b)Up in Friesland, tradition, at least of sea songs, is being revived mainly through the sterling efforts of Nanne Kalma, a songwriter of some power. Nanne has not only written some great songs in traditional style (one of them is sung by Johnny Collins on his last CD, translated into English - "She stands on the quay"), he has also written a number of musical shows highlighting pages of Dutch maritime history. And every October, in Workum, he runs a GREAT maritime song festival (Shantyfestival De Stront) timed to coincide with the annual "stront race" event for skoetsjies (the little Zuiderzee boats). J.Collins and Jim Mageean are regulars there, and so are Danny & Joyce McLeod, Graeme Knights, Shanty Jack etc. Such is Nanne Kalma's contribution to the traditional culture of Friesland, that he has been awarded the Dutch Medal of Honour by their Queen.

Now, that's something you don't see in England!