For 2009, the cost of a postage stamp started at $0.42. Starting May 11, 2009, the cost of a postage stamp rose to $0.44. The cost of postage stamps started May 11, 2009 per ounce was $0.44 each additional ounce was $0.17 and postcards were $0.28.
Cost of a postage stamp was dependent on the face value of the stamp and the country . The most common rate stamp is for First Class Mail. In October of 2004 in the US it was 37 cents for the first ounce.