The best one appears to be Wikia, which is a sister project to the well-known Wikipedia and uses the same excellent MediaWiki software. The downside is that they are a bit choosy nowadays — they're not just a no-questions-asked hosting service like PBWiki or StikiPad.
So I went ahead and filled out an application for a wiki on Wikia. Fortunately it's less imposing than, say, a grant proposal (have we categorized Filling Out An Immensely Complex Form yet?) Here's what I gave for the description:
A listing of, and analysis of, dream archetypes. Despite each person's dreams being unique, and resistant to understanding, they do seem to repeat common themes and plots -- The Forgotten Errand, Visiting An Unfinished House, The Gift From A Stranger, Returning To School, etc.
This wiki would be devoted to enumerating these, linking between them, and exploring them from multiple perspectives such as psychology (esp. Jungian), anthropology, folklore and literature.
This is not to be a simplistic "dream dictionary" that provides rigid interpretations of symbols; rather, it treats dreams as a universal shared folklore of the unconscious and seeks to describe and categorize this genre, much as the brothers Grimm and others did for the folktales created during our waking hours.
This project was recently begun by the writer John Crowley, who suggested the need for "a real taxonomy of dreams: not an analytic mode or method, we are far from that pace Freud and others, but a simple taxonomy, like the meme structure of folktales."  A LiveJournal community  has been created to continue listing and analyzing, but it's been noted  that a wiki is a much better medium for this than a shared blog.
Hopefully that will be erudite-sounding enough to snow them. I'll let you know; but it may take a week or so for them to get back to me. In the meantime, let's all keep dreaming!