2nd Gen iPod (iOS4.x) using iPod keyboard
The original article by Andy Ihnatko can be found here: The iPad Keyboard Dock works with the iPhone 3GS! According to one of the commenters there:


  The iPad keyboard dock also works with my iPod touch 2G (8GB) running iOS4. Great!


But personally, I'm not sure how or why this would be a better solution than a Bluetooth keyboard.