1. iPad Keyboard Dock: You need this if your going to use your new iPad with a physical keyboard. The keyboard dock also allows you to charge the iPad and has a 30-pin connector which let's you connect to an electrical outlet using a USB power adapter. It also sync's to your computer and use the other accessory the camera connection kit. You can also connect it to external speakers and listen to your music. Business users who would need a physical keyboard would definitely need to keep this on the iPad accessories list.
2. iPad Case: This case comes in very handy especially for those who are travelling. You can simply open the case and browse through your material or pictures and watch a video. Like the iPad the case can by used in various positions, horizontal and verticle
3. iPad Dock: If you think you do not need the keyboard dock and would be able to do all your work on the digital touch screen keyboard. Then you can settle only for the iPad dock. It has a rear 30-pin connector that lets you connect to a power source using the USB power adapter. You can also sync the dock to your computer, use the camera connection kit or play music on external speakers or a stereo.
4. iPad Camera Connection Kit: The camera connection kit gives you two ways to import pictures to the iPad from your digital camera. The kit allows you to directly import photos using the camera's USB cable or you can use the SD card reader to directly import videos and photos from your camera's SD card.
5. iPad 10W USB Power Adapter: This adapter lets you charge your iPad directly from a power outlet. It also comes with a 6 foot long power cable to increase that distance
So these are all the official accessories that are available for your iPad.
Source [ Apple ]