The Boy Genius Report suggests that the iPhone 3G may be made available for purchase in Best Buy and Radio Shack retail stores in the U.S. While the report stresses that this is an unconfirmed rumor, they do claim that their source has a good track record.
There is no word on whether the iPhone 3G would be available in these stores on the July 11th launch date or if there would be a delay before it makes its way to these additional distribution points.