Here it goes: http://www.apple.com/ipad/sdk/
The SDK is still in beta but if you want to get a head start and catch the wave while it’s still rising – now it’s the time. As the part of the package you get the iPad simulator, or as Apple put it:
(the simulator) lets you build and run your iPad application on your Mac, allowing you to lay out your user interface for the larger screen size, test your app’s memory usage, and shorten the debug cycle in the design process….
Needless to say there is a programming guide:
iPad provides new opportunities to create Multi-Touch iPhone OS applications on a larger display than ever. The iPad Programming Guide introduces new features available for iPad and how to implement those features in your applications.
And a Human Interface Guidelines doc
Design an incredible user interface and user experience for your iPad application by following the iPad Human Interface Guidelines. Learn how to effectively use the new views and controls available to you to deliver unforgettable applications to your customers.
The SDK allows you to crank out a single binary deployable on iPhone, Touch and iPad…
