Wikispaces

Wikispaces (http://www.wikispaces.com) is a free and painless way to set up a Wiki.

First things first: a wiki is set of easily created and edited, interconnected webpages that can be built by an individual or a group. At its broadest, it can be edited by anyone who visits the page (e.g. - Wikipedia). More commonly, editing is allowed only to invited Wiki members. Thus, you can create a Wiki about a specific subject, and invite group members to add pages or edit existing ones. It's a good way to gather and share information.

Wikispaces allows to to easily create new pages (by clicking the New Page button) or edit existing ones (by clicking the Edit button). Tools are clearly labeled, and a navigation bar to the left automatically add links as new pages are added. In addition, you can embed images, multimedia, Word documents, PowerPoint presentations, Excel spreadsheets, PDF files, links and more.

A "cheat sheet" for often used commands is available at http://www.scribd.com/doc/2238100/Using-WikiSpaces-for-Your-Eportfolio. The screenshots are a little old, but the information is accurate.

Below is a screenshot of a hastily assembled demo Wiki gathering information on one of my favorite topics. Link to it here.