Apple has posted an online database to allow potential iPhone 3GS customers in the U.S. to check stock levels for the various models at Apple Retail Stores. Availability is updated at least hourly. Apple deployed similar tools for both the original iPhone and the iPhone 3G, although these previous versions only updated nightly with stock levels for opening the following day.
Apple’s database is currently showing solid availability, with nearly 90% of Apple’s over 200 stores having stock of all four models. Only five stores are completely sold out of all models at the moment.