What is the best site to set-up a wiki for free?

When you say “private” do you mean that only your members can edit it, or only your members can view it?

If you’re okay with everyone seeing it and only members being able to edit, you can use the Free version of Wikispaces.com

@MrItty I am hoping that only my members can view it. I am ok with the members being able to edit it, I just want only the members to be able to access it. Thanks for the link, I’ll check it out!

@SuperMouse In that case, you might also want to check out http://www.wikidot.com/plans. They seem to offer private wikis for free, but they are also advertiser-supported.

Great link, thanks!

wikispaces is good. You can also host it in dropbox for free.