Favorite destination in the Netherlands?

Amsterdam is always a favourite. There's lots to do and to see , tours, canals , museums etc. However, for smaller towns and cities, I like Heemskirk. It's just off the main train line near Haarlem. There's a great youth hostel in a 14th century castle. There's a moat around the castle and a disco in the dungeon.
Newer 2 story accommodations are available on the property. I believe they have family rooms as well. It's well worth staying for a night.

My favourite town in Holland is Haarlem. It’s a quick train ride from Amsterdam and is absolutely gorgeous. The Shopping is great, the town square is always lively and the architecture is interesting. It’s a beautiful town to wander around without the hustle and bustle and tourists of Amsterdam.
Assumburg castle/hostel in Heemskirk is amazing and Dave is correct about the “Family Rooms” being available. Great place to introduce kids (and Opas) to the joy of Hosteling.

Domburg, on the tip of Zeeland's coast. Perfect little seaside resort.

Among countryside/out-of-town site, my absolute favorite place is the Kröller-Muller Museum (www.kmm.nl) which is also located within the Hoge Veluwe national park.

For pastoral loveliness, I love Friesland! My husband's family is from there and it is like something out of an old Dutch painting. Fields, windmills,canals, cows, farms with cheese to sell and really cute towns like Sneek, Leeuwarden, and tiny Sloten. Highly recommend the area!

Amsterdam. So much to see and do.

Amsterdam is my favorite place in Holland, But Haarlem is wonderful day trip from Amsterdam. It's an easy train ride and the city is great.

Delft is another great place to stay and/or visit..great canals, wonderful "old town"....and of course if you are into pottery, Delft Blue-ware.

I loved Delft most of all. My mother went crazy buying the Blue-White trinkets. Walking along the canals was nice and seeing the bridge was amazing. I also loved Kinderdijk.