This is based on a discussion in my 21st Century Learning Class:
I think Wikis are the poster childs for the entire concept of the Read/Write Web or AKA Web 2.0 (I personally dislike that term). The whole idea of making the web be the new OS, and be our applications has enormous possibilities. Wikis are the best example of this, they are a web page, a presentation, a word processor, all rolled into one.
But how does this make a difference to our students? By giving them the ability to 1) Create a webpage easily and effectively. 2) To share information with their group or classmates as a whole.
In regards to sharing information, have a wiki page for a subject in class, say the history of North Carolina in 8th grade, and build your own wiki page. Have students collect all the information they find into one resource to be shared. Not only have you created a worthwhile project that you can go back to, as a teacher you can view individual contributions and assign different grades for the same product! For those of us that love th concept of group work, but hate the grading of it - this is a lifesaver.
But, this brings up another point - how do we know the info in a wiki, such as wikipedia is factual? Well how do we know what is in Encyclopedia Britannica is factual? We place our faith in a few people that write for Britannica, and ASSUME that it is correct. Just because it is in print, doesn't make it any better, it just makes it harder to correct. Wikipedia depends on a community of people and corrections can be made easily, economically, and quickly. However, ALL sources, print, web or otherwise should be corroberated. In doing research, nothing can be taken for a fact unless two other sources can confirm that fact. Wikipedia nor should Encyclopedia Brittancia be our primary and only source for information - it should be a starting point, but not the be end and end all.
For reference, Nature did a study of Wikipedia vs. Britannica in 2005 http://www.news.com/2100-1038_3-5997332.html