Apple has announced the availability of iPhone SDK 3.2 Beta for developers to make sure their apps are ready for iPad, iPhone and iPod touch when the iPad is released in exactly two months from now. Members enrolled in the iPhone Developer Standard or Enterprise Program can access the development bits for iPhone OS 3.2 Beta for iPad by signing into Apple Developer Connection.
The new SDK which includes iPad simulator, iPad programming guide, iPad human interface guidelines and iPad sample code for the moment atleast is for iPad only. The release notes clearly states: "iPhone OS 3.2 does not support iPhone and iPod touch devices. It runs only on iPad."
UPDATE 1: Some features of the new iPhone OS 3.2 has been unveiled from the SDK. More info here.
UPDATE 2: iPhone OS 3.2 and SDK for iPad has gone Gold Master! More info along with download links can be found here. [iPad Only Release]