from http://www.alt-usage-english.org/excerpts/fxputino.html This expression meaning "to contribute one's opinion" dates from the late nineteenth century. Bo Bradham suggested that it came from "the days of $.02 postage. To 'put one's two cents' worth in' referred to the cost of a letter to the editor, the president, or whomever was deserving". According to the Encyclopaedia Britannica, the first-class postal rate was 2 cents an ounce between 1883 and 1932 (with the exception of a brief period during World War I). This OED citation confirms that two-cent stamps were once common: "1902 ELIZ. L. BANKS Newspaper Girl xiv, Dinah got a letter through the American mail. She had fivepence to pay on it, because only a common two-cent stamp had been stuck on it." On the other hand, "two-cent" was an American expression for "of little value" (similar to British "twopenny-halfpenny"), so the phrase may simply have indicated the writer's modesty about the value of his contribution