wikispaces.com

Pros:

 * ======You can add people to your wiki, allowing them to edit it ======
 * ======You can personalize your website ======
 * ======You can embed videos, spreadsheets, calendars, etc. ======
 * ======You can email your collaborators ======
 * ======Auto-saves ======

Cons:

 * ======The page sometimes changes from how it looks in editing when you save ======
 * ======Editing tools are frustrating ======
 * ======Images can't be dragged and dropped everywhere ======

I give Wikispaces 3.5 stars!
+ .5