Dutch Folktale Database (Nederlandse Volksverhalenbank) of the Meertens Instituut: www.verhalenbank.nl
Dutch Song Database (Nederlandse Liederenbank): www.liederenbank.nl
Global Folktale Almanac (Wereld Volksverhalen Almanak): www.beleven.org
Holy places or places of pilgrimage in the Netherlands: www.meertens.knaw.nl/bedevaart/
Family names in the Netherlands: www.meertens.knaw.nl/nfd/
Objects mentioned in Dutch probate inventories from the 17th–19th century: www.
meertens.knaw.nl/boedelbank/index.php
More databases: follow the link