Apple has been officially awarded the "IPHONE" trademark in the U.S. Patent and Trademark Office under number 3,746,840 covering International Classes 9, 28 and 38.
Of interest from the award which covers both the name and logo is that the trademark includes classes 9, 28 and 38. The most interesting of the three being class 28 which covers "Handheld unit for playing electronic games."
View the full patent certificate here, awarded on February 9, 2010.