I just found out a superb free wiki provider - wikidot.com. It's quite new so great domain names are still free. I just registered http://linux.wikidot.com

The Wiki is ajax-powered, offers quite easy way to customize and has a few great features not found anywhere else, like:
- option to register an additional domain name for the site, i.e. getlinux.info (the site would be then available both from linux.wikidot.com and the additional address)
- nice editing options
- easy way to share the wiki (allow others, either registered or anoonymous to register)
- google ads for both the provider and the content-writer (not tested, yet)
- easy google analytics integration (I just set it up)
- much much more

You can test it yourself and say what you think about it.
Cheers