Earlier this year, I attended a workshop by Caroline Musselwhite. Other than being an absolutely engaging presenter, I learned quite a lot. One of her main points was that all students (with or without significant cognitive disabilities) need three types of reading materials - Enrichment, Transitional, & Conventional. Here's a .pdf that talks about the process of creating and using these types of books. The chart at the end of the file:
Beginning Literacy Framework
This was created by Caroline along with several other people at Don Johnson. Check out Caroline's site AAC Intervention. She has monthly tips on how to get more literacy into your day.