All of the built-in apps on iPad were designed from the ground up to take advantage of the large Multi-Touch screen and advanced capabilities of iPad. And they work in any orientation. So you can do things with these apps that you can’t do on any other device.
Mail
There’s nothing like the Mail app on iPad. With a unified inbox, split-screen view, and expansive onscreen keyboard, it lets you see and touch your email in ways you never could before.
PHOTOS;

With the built-in Photos app on iPad, you can see and touch your photos in intuitive new ways. Your photo albums appear as tidy little stacks you can pinch to preview. Tap a stack, and the whole album opens up. From there you can scroll through thumbnails. Tap to view full screen. Or flip through photos one at a time.

The gorgeous 9.7-inch iPad display shows off your photos in vivid color with excellent brightness and contrast. It uses a premium technology called IPS (in-plane switching) to provide an extremely wide viewing angle, so friends and family can crowd around your iPad and still get a great view.

When you rotate iPad, your picture rotates, too, so you can show it off any way you want. Flip iPad over to share a snapshot with the person across from you, then flip it back to share with someone sitting next to you. You can even create and play your own slideshows, complete with music and animated transitions. Place iPad in the optional iPad Dock, turn it on, and enjoy the spectacle from across the room. When you want to share photos from afar, email them or publish them to the web using MobileMe with just a tap or two.1