Voice Dream
Voice Dream offers a reading and a writing app that are spectacular. You can save yourself a little money if you are interested in both the reading and the writing apps by purchasing the bundle upfront. The Voice Pack that is included with the bundle will give you access to the "James" voice, which happens to be my favorite.
Voice Dream allows you to change the text to meet your reading needs (colors, fonts, etc) as well as listen to the text with high quality voices. A large variety of file types are supported.
Voice Dream Writer allows you to speak your text and offers a variety of high quality editing tools that allow you customize your writing experience.
FineScanner Pro
http://www.abbyy.com/finescanner_ios/
FineScanner Pro allows you to snap a picture of text and run high quality OCR right on your iPhone. The text can then be "opened in" Voice Dream Reader. Photos of your document must be taken within the FineScanner Pro app - you may not import a photo for OCR.
Scanbot
Scanbot is an alternate scanner/OCR app that has an educational version (no in app purchases). While it isn't quite as refined as FineScanner or Prizmo for text to speech usage, it does provide a spectacular scan that you can read in app using Apple's text to speech features for very little cost.
Prizmo
http://www.creaceed.com/prizmo
Prizmo provides an all in one snap, OCR, and text to speech option. The quality of the OCR is high. The voice quality is not my favorite. It is fast, however. To date I have not found an easy way to send text from Prizmo to Voice Dream.
Apple
http://www.apple.com/accessibility/ios/#learning
iOS devices (iPads, iPhones, and iPods) have accessibility tools built into the operating system. See Apple's webpage for their most recent offerings.