As of March 2010, each letter or card is 44cents. If you use a square envelope (4 x4 or 5 x 5 for instance), it's another 20 cents.
That will depend on where in the world you are posting it from.
+98
Postage for greeting or postcard from Australia to UK is A$1.60 as of December 2011.
It's $1.25 for a greeting card.
It typically takes one international Forever stamp, which is currently priced at $1.30, to send a standard-sized greeting card to Germany. However, it is advisable to double-check the current postage rates with the postal service before sending.
As of April 2009, the postage to send a square greeting card is the standard first class 1oz letter postage of 42 cents, plus a non-machinable charge of 20 cents.
Buy a card. Write your greeting, Place card in envelope. Buy the correct postage. Insert card in postbox
$1.80
It depends on where you are posting it from and where to - nationally or internationally.
If it is a US unused stamp, it is worth at least 3 cents for postage. With identification, using a catalog, it may be worth more. A few minutes with a US catalog, often available in your local library, will help you determine value.
The postage rate for sending a package or envelope to Madrid, Spain will depend on the origin of the sender. It will also depend on the choice of options as to how fast the mail will be sent, whether it is express or regular mail.
Via USPS:1oz or under - 94¢2oz - $1.743oz - $2.54(Side note: In general, most letters and greeting cards seem to be at or below 1oz. Every greeting card I've ever sent in my life has been 1oz or under. Basically, if it's a letter/card that you'd probably use a single First-Class stamp for within the US, it's probably 1oz or less and would currently be 94¢ to send to Japan.)This is all subject to change when postal rates increase, as they do from time to time. So keep an eye on the United States Postal Service website for up-to-date rates.