Educator Christian Long writes on using Wikis in the classroom. I'm not an educator, and my kid isn't one of Mr. Long's students, but I sure would like to see similar tools used in my kid's school. I'm not sure how particularly useful they would be in kindergarten, but editing that linked article as a class project would be fun.
That said, how likely is it that students are interested, under their own power, in editing a wiki? Based on my experience that only about 5% of readers tend to be contributors, I think it might be difficult - but of course, the percentage in an English class might be higher. Students around here are asked sometimes to edit Wikipedia or Bloomingedia as a class assignment; for example this article:
was obviously written by a local teen. But if you look at the contributor's history, he copied in the bulk of the article on March 30th, came back and fiddled with it a few days later, and then never came back again.
Now, Mr. Long isn't having his kids put their essays on the wiki - at least not yet! But if, or when, it occurs, I wonder whether an English class discussion wiki would really work on its own terms without constant prompting by teachers. I suspect it could, if it is linked to the real world somehow. I'll be following the experiment with interest.