Using the application Text Edit (small word processing app similar to Windows Word Pad) – check out the Services menu.
Paste source text from a website, online book, or other text into a Text Edit document. Under the Text Edit > Services > Speech > Start Speaking Text. Let the computer read the text. Check out this screencast.
Take that idea one step further. If your students needs to listen to an article at a later time, create a podcast of a section of a book or an article. Take a look at this article about how it can be done.
The Text Edit program can summarize a large source text. After a set of text is pasted, highlight it, and then under the Text Edit > Services > Summarize. You can control how short the summary will be. High light a couple hundred words and the computer will summarize it into a sentence. Pretty amazing! Use this strategy to help students with reading comprehension. Perhaps it may also be a way to analyze their own writing. Use the summarize feature to check the message of an essay. Take a look at this screencast.
Both these features also work with Safari. Safari can read the text of a website as well as summarize a section of text.
Press and hold Apple+Control+D over any word in the Safari application and up pops a handy dandy Dictionary/Thesaurus.