FLAG
The Dutch flag is a tri-color emblem of red, white, and blue- in that order. At first I thought it was a pretty lousy flag; boring and virtually identical to the French one (except the Dutch stripes are horizontal). However, over time I have grown to appreciate it, and now I actually think it's a pretty good flag for Holland. As far as I am aware the colors don't actually mean anything, and are just an adaptation of an ancient heraldic crest of some sort. The colors are used a lot in advertising and marketing however, and often when a Dutch company wants to market something as authentically Dutch, the packaging will incorporate some version of the red-white-blue motif into its design.

The Dutch are not overtly patriotic, except on special events. As a result, the Dutch flag is not a very common sight in Holland, and is usually only flown from political buildings or tourist attractions. The other most common location of the flag is on the back of Dutch boats. For centuries Dutch sailors have fastened a flag to a short pole at the back of their ship, and the tradition remains widespread to this day. No matter how small or unassuming a boat may be, if it's Dutch nine times out of ten you can guarantee there'll be a flag on it.

ORANGE
The name of the Dutch dynasty that has ruled the Netherlands for most of its existence is the House of Orange. In many ways the history of the House of Orange is synonymous with the history of Holland, and as a result the color orange is one of Holland's proudest national symbols. On patriotic occasions, such as the week of an important soccer match or the Queen's birthday, the color orange will appear everywhere, in the form of banners, t-shirts, facepaint, balloons, giant novelty hats, and even fountain dye. It can get a bit tacky at times.

NATIONAL ANTHEM
The Dutch national anthem is supposedly the world's oldest, but it's also one of the strangest. It's basically just a short autobiographical summary of Prince William of Orange, as sung by himself. So when you sing the Dutch anthem you are essentially speaking as the prince, which sounds a bit odd. Here are the lyrics, literally translated:

William of Nassau,
Am I, of German descent
Loyal to the fatherland
I will remain until I die
A Prince of Orange
Am I, free and fearless
The king of Spain
I have always honored

MONEY
As is the case in most of Western Europe, the Dutch currency is the Euro (€ ). Previously the Dutch currency was known as the Guilder (abbreviated as "fl" for some reason), but from 1999 to 2002 it was slowly phased out. You still sometimes see Guilder prices listed alongside Euros for comparison. Euro bills are all very bland and undistinctive, because they are used in many different countries and thus can't have any pictures that would be seen to favor one country over another. The Euro coins, however, all have different images on them. Dutch Euro coins always feature a highly stylized portrait of Queen Beatrix on the reverse. It's very common to get Belgian and German Euro coins mixed in with the Dutch change, so the occasional German eagle or fat Belgian king are not uncommon sights either.