I’m still browsing for a new wiki home myself, but I think that Xwiki (http://xwiki.com) looks promising. Darren Kuropatwa is running a couple of interesting wikis over there if you’re interested in taking one for a test drive. http://bprime.xwiki.com is the URL.

Darren’s wiki is worth looking at, anyway.

For hosted wikis, I am liking the looks of WikiSpaces http://www.wikispaces.org/ which has everything you asked for except password protection.

I though that Web Collaborator also was a good wiki/blog creature that was not laden with techie terms:
http://webcollaborator.com/

However, to get the specific features I would think you have to run one on your own servers.

TikiWiki (http://www.tikiwiki.com) has worked great for me. Now it isn’t a service (like blogger), you have to install it on a server with MySQL and PHP, but the install tool does almost all the work. Plus. it’s not just a wiki, but a CMS with the main section being a easy to use Wiki. I have used it for two projects with my sophomore world history students. The big key is password protected, that way I could track who was changing what pages. I’d love to say I trust my students…

The projects:
Holocaust Wiki Project – http://www.ahistoryteacher.com/holocaust
WWI Battles – http://www.ahistoryteacher.com/world

A bunch of us have been using Wikispaces for the past month or so working on BlendedLearning: helping educators get started with some of the free and easy tools on the web (blogs/rss/etc). As Alan said, Wikispaces has nearly everything that you’re after… although it does have google ads along the side.

It also has built in Creative Commons licensing, which is a plus for us, but may not be what you’re after.

I’ve been using WikiSpaces also to post presentations. It’s really easy to use, but it doesn’t have password protection.

I’ve recently stumbled upon a new one called pbwiki – it’s password protected and looks promising.

Update: Oops! Forgot that Wikispaces has Google Ads. I use the Adblock extension in Firefox so I never see them!