At this moment, there’s a poll on this website to see which province the ancestors of our visitors come from. To my surprise, Limburg is in the lead! Perhaps because my own research is focused on Dutch Reformed regions, I had never realized that many people emigrated from the catholic region of Limburg as well.
I did some Googling and found a great resource for Limburg emigration research: the Limburg emigrant page. It has background information, census records, emigrant letters, you name it.
Based on this information, I updated the Limburg-article in the Netherlands/Geography section. I will try to find more information on Limburg in the next couple of days.