For a first class letter of one ounce, as many as it takes to add up to 98 cents of postage.
As of January 22, 2012 the rate is 45 cents. You could also buy the "forever" stamp which will never lose its value as a current stamp.
Market is about a dollar or so. The amount of gold is so small that it isn't measurable. The fact it was mailed is not terrible, but does reduce the value.
The H stamp was the one with the Hat on it. It has a face value of 33 cents.
A book of stamps to be used for postage is called a booklet. A book used to hold a stamp collection is called an album. One used to identify and value stamps is called a catalog.
4 cents. Put it on your next letter.
That stamp was issued in 1985. It has a face value of 22 cents.
A G stamp has a face value of 32 cents. You would have to add 27 cents to mail a letter with it.
It depends on the weight of the letter and the value of the stamp you buy.
The F stamp was a picture of a Flower. They matched the picture to the letter. It has a face value of 29 cents.
Five cents was the value. That was the cost of mailing a half ounce letter.
Of course the value will depend on many variables. A typical postcard should be worth $5 if it was mailed from a soldier overseas. A postcard with a photo may be worth more. Some cards with a commercial Logo such as Coca-cola might have a special interest to collectors. I have a post card mailed from Stalag IIb that has a German stamp and an ink stamp of the prison camp and I would expect it to be worth $25 or as much as $40.
The tulip stamp was marked as the F Flower stamp. It has a face value of 29 cents.