John Larmer sees a sliding scale: "There is a sliding scale of authenticity for projects, which goes from "not authentic" to "somewhat authentic" to "fully authentic.""
Insert a URL on this page and it will render a readability score using Flesch, SMOG, etc., plus statistics such as number of words, sentences, etc. This could be helpful to determine readable authentic materials for ESL/EFL learners. However, I suspect most webpages all run pretty close to the same level. This would be interesting to experiment with, and especially useful for electronic books and content materials.
"The U.S. Library of Congress offers a wealth of fantastic online resources for teachers and students. A quick jump into the teachers resource page will lead you to things like these primary source analysis guides that I have used with students in the past. The LOC also offers a couple of good iOS apps that are worth noting."
Shows how various apps can be used with the teachers' resource pages at the U.S. Library of Congress. Great authentic materials for research papers and projects.
H/T to R. Byrne