I am considering a "Christmas" vacation in The Netherlands later this year and am looking for late-November through Christmas-time locations, events, festivities, and any lodging tips from seasoned travelers.
The Dutch observe Sinterklaasavond (Dec 5th) and Christmas (Kerst, in Dutch) both, but there is something special about Sinterklaas and it's a bigger holiday, really. I would suggest that as your focus. That would be mid-November to December 6th or so. I'm not sure I can suggest any one place that is an epicenter of Sinterklaasavond, it's celebrated everywhere.
The key festive weeks are the ones leading up to Sinterklaasavond. First you have "the arrival of Sinterklaas in the Netherlands" in mid-November, as he "arrives from Spain" on a steamboat. Decorations are put up for the season and the special foods appear if they haven't already. I think there are celebrations in all major cities and towns, but there's always one that's "official." Last year it was Groningen, I don't think 2014 is decided yet. There will definitely be an enormous to-do for his arrival in Amsterdam.
After he arrives, there are various parades and appearances that spring up - you will occasionally see people walking around or in parades dressed as Zwarte Piet, which is always a bit of a jolt. You'd have to look things up for the area you're staying in. Holiday treats abound in the shops and there's a lot of people shopping for gifts.
That's all over Dec 6th, but there will be some outdoor Christmas markets that spring up - look up 'Kerstmarkt' or look for flyers wherever you are. They are typically small. Stands pop up selling oliebollen - donuts - and if you ever see stands selling hot stroopwafels, those are fantastic. Christmas isn't such a big deal in the Netherlands, but there are plenty of cultural events over the late fall/winter season.