A new carrier file has been added to iPhone 4.0 Beta 4, now version 6.2 up from version 6.0, that has brought back the hopes of native tethering for iPhone users on the AT&T network.( Something every other network has already been enjoying).
AT&T tethering
Posted inHOWTO
HowTo: Enable Tethering in iPhone OS 3.0 Using MobileSafari ( AT&T )
Instructions on how to enable tethering for users on the AT&T and other networks using MobileSafari.