Mac Rumors reports that Apple has released iOS 4.0.1 for iPhone 4, 3GS, and 3G

As predicted earlier today, Apple has released iOS 4.0.1 (8A306) for the iPhone 4, 3GS, and 3G. Details of the update are as yet unknown, although it is presumed to address the signal strength indicators as promised by Apple earlier this month

  Apple Releases iOS 4.0.1 for iPhone 4, 3GS, and 3G