School Mediation Associates, an organization located in Massachusetts, offers mediation services, training programs and book/video resources concerning peer mediation.  As a side note, I have featured two of Richard Cohen's books on the site, which can be found in the resources section!  The organization also authors a seasonal newsletter and has provided links to its archived articles:

http://www.schoolmediation.com/newsletters/index.html

In addition to perusing the archived newsletters, you can search by topics, which run along the right side of the page and will like to articles written on a specific topic.  Finally, School Mediation Associates offers a free email newsletter, which you can request on the main page.