CNBC states: "3G iPhone is set to hit store shelves by late May or early June 2008".  They cite sources close to Asian manufactures that are working with Apple. Steve Jobs has stated that a 3G version of the iPhone is under development and will be available in 2008.  The CNBC report gives us insight that it will likely be in the first half of next year.

Video
You can view the report by Jim Goldman at CNBC here.  Also in the video, details about the long rumored 12-inch ultra portabe Mac notebook.

What is the iPhone?
The iPhone is a mobile phone designed and marketed by Apple Inc.  Apple markets the iPhone as a "Revolutionary Phone", "Widescreen iPod", and "Breakthrough Internet Device".  The iPhone was announced and demo'd by Steve Jobs at MacWorld 2007.  The iPhone was first available for purchase in the United States on June 29, 2007 and later became available in the United Kingdom, Germany and France in November 2007.

The iPhone supports the GSM standard.  You can learn more about the iPhone here.