Samantha Roslund has written Join Forces: Teaming Up Online, a book that explains the benefits and features of collaborative online work.
Written at lower elementary level, this book would probably work best with fourth grade. I suggest using it to introduce the digital concept right before starting a large collaborative project. If the teacher has already established a class Wikispaces with parameters, then the book becomes a helpful student resource.
For the more ambitious student, they could use the book as a guide to set up their own personal wiki. The book includes ample reminders to stay safe online and how to create quality content. Activities reinforce written content and the glossary/index keep everything organized. Schools might consider purchasing enough copies for an entire class so that multiple students have access to this resource.
Disclosure: I received a copy of this book to review from our school librarian but I was not financially compensated in any way. The opinions expressed are my own and are based on my observations.