Apple retail stores will be open at 8 a.m. local time on Friday, July 11th to support the official release of the iPhone 3G. Last week, AT&T confirmed the 8 a.m. launch along with other release details.
You can find the nearest Apple Retail Store or AT&T location at their respective websites. If you have questions regarding upgrade eligibility or becoming a new customer, AT&T has put together an iPhone "What you need to know" section offering answers to common questions. You can also download their iReady checklist.
Source: http://www.everythingicafe.com