Larry Ferlazzo shared this link to an Ed Week commentary on Wikipedia. There's a lot of good stuff here, including ways to help students get the most out of Wikipedia as they do research.
I used to be rabidly anti-Wikipedia. I remember frothing at the mouth while telling my students of the evils to be found at the site (peppered with tales of high-profile news stories about contributors with false identities). My students would quiver in fear and shrink from my wild gesticulations.
I'm over all that. Now when I talk about using Wikipedia, I talk about it in much the same way that Matthew Shapiro, the author of the commentary, suggests. Wikipedia is a place to start, but there are many additional and valuable resources out there.
Here's a thought for schools....Wikipedia might be BETTER than a traditional print encyclopedia for students. Why? It's more up to date. The Brittanicas in my site's library are nearly 10 years old.