This is your official post telling you about the upcoming postal rate changes that will be effective starting May 14, 2007. The USPS website lists things here; I recommend you read it.
The quick-and-dirty guide to the rate change:
US domestic first-class mail LETTER: 41 cent stamp
US international first-class mail LETTER to Canada: 69 cent stamp
US international first-class mail LETTER to almost-everywhere-else: 90 cent stamp
There are now different size-based rates for mailing LETTERS, FLATS, and PARCELS. This is why you should read the website I have linked to... they do not all cost the same anymore!
IF YOU ARE SENDING ME A SNAIL MAIL QUERY, ASSUME THAT IT WILL NOT BE ANSWERED UNTIL AFTER MAY 14, 2007 AND PUT THE CORRECT POSTAGE ON IT. OTHERWISE, IT WILL NOT BE ANSWERED.