As a part of today's Apple media event, the company has released a new update to the iPhone SDK, in order for developers to take advantage of the new features found in the iPad.
The new update features, as you'd expect, the ability to build and run applications on the new Apple device, either on the iPad itself or in a simulator. Although the iPad can take advantage of the current applications on the App Store, it makes far more sense to allow your app to take advantage of the higher resolution. We haven't had a chance to have a play with the SDK yet, but as soon as we can, we'll update this page with what we can. Keep in mind that there is an NDA with it, so discussions will certainly be limited.
If you're a developer, you can expect to get this from the usual area, though if you're not a member of Apple's development community, you can still download the SDK for free from Apple. Please remember that this will mean you can only run applications in the simulator, and you have to be running OS X; in order for you to be able to build and run applications directly on your device, you'll have to be a member of the developer program. There was no iPhone OS update released, though now that the 3.2 update has been pushed, perhaps we will see one very soon.