Upcoming article for PC Magazine Philippines, entitled Build a Web Site Quickly with PmWiki:
Whether researching the scholarly (like the reason behind the Sistine chapel's name) or the trivial (the title of the third episode of say, "The Six Million Dollar Man") one of the first resources that the Internet-savvy turn to is the Wikipedia. In a span of a little over five years, the free online encyclopedia has grown to over five million articles in several languages, including 1.4 million articles in English.
How did the Wikipedia grow so quickly? For one thing, any registered member -- and that means anyone who cares to register -- can add, edit, or even delete pages from the Wikipedia. It's for this reason that traditional educators doubt the Wikipedia's accuracy and neutrality. But no one can deny that its open editability is also its main strength.
The underlying concept beneath the Wikipedia is, as its name suggests, a wiki. A wiki is a kind of website for collaborative authoring. Any word or phrase in a wiki article can be tagged to become a link to another article. It's in this fashion that Wikis grow over time.
Simplicity is key in wikis. Its goal is to make it easy to write entries. No knowledge of HTML is necessary. Instead, wikis use a simplified markup scheme for formatting and linking. For example, double brackets around a word, like [[this]], would turn that word into a link to another page.
Not all wikis have to be freely editable by everyone. Wikis might restrict membership to a group of people, say, team members on a project. Regardless, wikis usually employ some form of version control that lets an administrator restore the previous version of a page. It's a useful feature to have that protects to some degree against vandalism.