A PersonalWiki for iPhone and iPad. http://www.jera.com/wikipad/
The following relates to the old Palm OS version (still available at http://www.jera.com/wikipad/palm/ )
Instead of hyperlinking Memo and To Do items, the application itself holds all of the text that you enter. Despite this limitation, an initial test of the free beta shows that it is excellent for starting a wiki on your handheld immediately. Minimal complexity but available now.
There seems to be no provision for exporting your work.
WikiPad has gone non-beta in July 2004, is still free and it no longer has an expiration date. (Older versions were beta-only with expiration dates.)
WikiPad does not have a Back button, that I can see. Instead it uses a go to button which lists all the pages. This works ok for a small number of pages, but for heavy duty use a Back button would work better. Since there is no desktop version, WikiPad should provide a function to export wiki pages as text or memopad files, and an import function to import properly formatted text files.
Not to be confused with WikidPad, another PersonalWiki, in case that's what you were looking for.
SeeAlso iPad