This is an exercise I used last year with a lot of great results. I plan on using it again this year because it worked so well.
One of the most basic forms to establish that a student has comprehended their reading is to have them write or explain a summary of their reading. In order to write a summary, students have to read the text, process it and then put it into their own words. Students who can't summarize will simply read you a couple of lines of text if asked to give a summary.
So what do you do for kids who hate summaries or have a hard time understanding how to do it? Have them tweet it. Now, I don't have them actually use Twitter. Even if I wanted to, it's blocked on the school network. However, many students understand the general idea of Twitter and Facebook statuses. You can use this to have your students write tweets for a character in the book. If you want, you can have a group of students participate and reply to one another's tweets as the different characters.
There are a couple ways to readjust this type of activity for different disciplines. For history classes, students can tweet what historical figures are thinking about their latest adventures. In science, they can tweet the results of different experiments. In language classes, you can take actual tweets from whatever language you teach and have students translate them. This would be a great time to bring in how text language works in different languages, like Spanish speakers using "k" for qué (what). The only subject I can't figure out how to tweet for would be math.
In addition to helping students process language, this type of activity can have the fun factor. You're using something technology based and current! And you'll amaze your kids by actually knowing what Twitter and Facebook are. Everyone wins!