A wiki is a type of collaborative website with integrated tools for adding and editing content. The online encyclopedia Wikipedia.org is one popular example, WikiHow.com is another. But not all wikis give public editorial rights as Wikipedia does. A wiki can also be created for a classroom or a club, with an administrator who decides what pages are editable, and who can do the editing. Learn more about creating wikis at the following sites.
Although they do not call themselves a wiki, Google Docs provides a powerful set of collaboration tools, a familiar interface, and meets most of the usual wiki criteria. With a free Google account, you can post and share documents, spreadsheets, and presentations. As the document owner, you control who can view and edit each document. Since the documents are stored remotely, they are accessible from anywhere; and changes made by anyone, are immediately available to everyone. Forget the old paradigm of email, edit, email. Google Docs is a revolution in cooperation.
PBWiki provides anyone a free wiki website for up to three users, but educators get a special deal: a 10MB wiki for an unlimited number of users for free. Key features include speedy setup, an audit trail of changes made to the wiki pages, RSS and email notification of wiki updates, IP whitelisting and blacklisting, and four roles to control access: Reader, Writer, Editor and Administrator.
With drag-and-drop simplicity, PikiWiki is the easiest wiki to learn, and a great one for elementary-age kids. Not only is PikiWiki, free, but you can even build your first page without any registration. I recommend using Internet Explorer, as I had some difficulty using the site with Firefox. "With PikiWiki, even novice computer users can create unique, expressive web pages by dragging and dropping pictures, video, or any other media into their browser right from their computer desktop. ... Friends and family can similarly contribute to your page or create their own pages for you to contribute to."
The Wetpaint platform rolls features from wikis, blogs, and forums into what they call "your own social website." Wetpaint sites are free (for everyone) and you can get yours up quickly by starting with one of their pre-populated templates built for classrooms, group projects, sports teams, or book clubs. For teachers, they have a special page about Wikis in Education and an Educator Ambassador to personally answer any questions you might have about using a wiki in the classroom.
Wikipsaces is another wiki platform with a special offer for teachers. Since 2006, they have given away over 100,000 wikis for K-12 education, and have announced a goal of adding another 250,000 to that number. For those of us who are not teachers, Wikispaces has a free option (a 2GB public wiki with unlimited users) or a tiered pricing plan based on which advanced features you need.