The postage rate (not 'porstage' rate) for stamps in the United States varies depending on the type op mail you would like to send. For regular letters the postage rate is 46 cents plus an extra 20 cent for each ounce.
The basic rate for US first-class stamps is currently 44 cents.
There really is no 2nd Class postage stamp. Stamps are issued in multiple denominations to cover any rate necessary. While the bulk of stamps sold are those that match the first class rate, you can buy them in a wide variety of values.
As of March 21, 2013, the current US postage rate is 46 cents for letters that weigh 1 ounce or less. Additional ounces cost another 20 cents. International letters cost $1.10 an ounce. A good idea is to buy so called Forever Stamps, which can be used forever.
The US has issued many 5 cents stamps. I believe the most recent pictures a canoe. It was the postage rate from 1963 until 1967.
You use the stamps of the country of origin, which in this case is the US. So the individual pays the rate in their country and their countries postage is affixed to the item.
Priority Mail flat rate envelopes cost US$5.75 in postage. With standard 49 cent stamps, it would take 12 stamps to cover the postage.
The US domestic rate for an ordinary 1st-class letter was 32 cents in 1996.
Forever stamps have the value of the current First Class Postage Rate. Currently they cost 49 cents. They can be used 'forever' to mail one ounce of US Postage.
The rate is 98 cents for an ordinary letter. You can buy 98-cent stamps, but any combination of valid US stamps that 98 cents or more will work, eg two 44's plus a 10-center.
These are the new Forever stamps issued by the United States. They are good for the first ounce of First Class mail. It does not matter what the rate is, you purchase them at the current rate. Even if the postage rate goes up, it is still valid.
The US domestic rate for an ordinary 1st-class letter was 4 cents in 1960.
The US domestic rate for an ordinary 1st-class letter was 5 cents in 1965.