Good old Saint Nicholas is the patron saint of the children, and many countries have some tradition of giving presents to children around his name-day (5-dec). But nowhere else are the festivities that extensive as in the Netherlands. The full 3-4 weeks between his ceremonial arrival from Spain and his name-day (and sudden back out) are a source of great fun for children and great stress for the parents, but also the other way around.
As salaction says, there is a lot of discussion about his black helpers. Radical 'Kick out Zwarte Piet' activists are opposed to people fiercely defending the tradition, and the place and time for confrontation are not always happily chosen. At the same time, it is my impression that the vast majority of the population wouldn't mind if black Pete would be any other colour (rainbow Pete), or just having traces of soot on the face (soot smear Pete - soot because the traditional story says that the helpers enter houses through the chimney to deliver presents). The tradition needs revision to remain the magic party for the children, but it will survive, I'm sure.
Because of all the attention going to Sinterklaas in early December, the Netherlands never had a strong tradition of giving presents at Christmas. This is gradually changing under pressure of globalization. But still, during the Sinterklaas period, you'll find him everywhere around, alive and all, while Father Christmas is still a pretty rare sight in the Netherlands around Christmas time.
It is quite a common pattern now that families celebrate Sinterklaas when the children are young and switch to giving presents at Christmas time when the children grow older. And returning to Sinterklaas again when grandchildren take the stage.
Santaclaus is actually the Dutch Sinterklaas celebration hijacked by Coca-Cola.