$1.15 for a letter of up to one ounce.
postage needed for A09 envelope
3
As of March 20, 2014, it is $1.15
Domestic postage is $1.39 for an ordinary envelope of uniform thickness.
21p
44 cents
Postage to Europe from the US is 98 cents for a one-ounce letter.
44 cents
96 cents.
See: USPO website.
Florida is in the US...
In the US, $1.56.