Nice!
I don't know if you already visited the standard tourist locations and I don't know what you like, but here goes:
Rijksmuseum, Amsterdam.
If you want to see windmills, go to the Zaanse Schans (very touristic!)
If you like 'old city centers' you can go to Delft, Leiden or Dordrecht.
Gouda (city of cheese and stroopwafels; buy both!) is also nice. My parents in law live there. The city hall is amazing. Go there when it's dark. There is also a winter fair on this weekend (starting on Friday).
Rotterdam is also very nice, but more modern.
You could visit the old fishermans town Volendam (near Amsterdam). It has an old harbour with small houses. From there you can take a boat to the island of Marken.

Enough to do!