Go to the USPS web site. You want publication 604a, which shows all of the non-denominated stamps issued by the US Postal Service.
It depends entirely on the value of the stamps. In 2010, a standard letter currently requires a stamp or stamps to the value of 60c within Australia.
The number of stamps that you need to send a letter from Australia to London, will depend with the value of one stamp.
The best way is to consult the USPS web site. They list all of the stamps issued without a value. These stamps can still be used for postage at that value, so other stamps have to be added. They can only be used for US addresses.
It depends on the weight of the letter and the value of the stamp you buy.
Your answer depends on the size and weight of the letter you want to mail. You can use the online calculator, below, from the USPS, to determine the value in stamps required to mail your letter.
Yes. Postage does not have to paid through individual stamps; as long as the value of all stamps placed on the envelope is enough to cover the cost that envelope carries, any number and value of stamps can be used.
There are many ways one can learn the value of stamps from Japan. One can learn the value of stamps from Japan at popular on the web sources such as Baxley Stamps and Herrick Stamps.
Yes of course, provided that it has the proper value of postage stamps on the letter.
No you cannot use them. Forever stamps can only be used for domestic (inside the US) mail. They must have a value on them for international mail.
All stamps are collectable. Whether they have value will depend on many factors including age, condition and rarity.
That is what the US issues stamps for, so that you can send mail to anyplace in the world.
Just one, as long as it is of the right value.