I know this might be difficult thing to ask for, due to the varying requirements and uses of PersonalWikis, but here's a seed wishlist for the features and characteristics of an Ideal Personal Wiki:
Use plaintext wiki pages
Allow at least basic formatting
URL and file linking
Allows export to html - both of the entire wiki or 'subnodes'
also allow some kind of mindmap / flowchart / network diagram view (see sdidesk for an idea) (even better put CamelCase on a network link and it jumps to the page. Also use includes to get diagram and linked text on a page.
Allow the configuration of the plaintext wiki page extension (for use with less flexible wiki tools)
Allow for definitions of Interwiki-type standards (this could allow you to use Interwiki syntax to access external applications)
Allowing for the creation of categories (possibly using folders)
Allowing the use of filesystem folder structures. This would essentially allow the benefits of a hierarchical structure. (This would probably be terribly difficult to implement - and I'm not sure if it's possible to do without compromising the WikiNature.)
Some sort of wiki journal functionality - something like EmacsPlannerMode?
Encryption to store passwords and other sensitive data
To Be Perfect:
Software released under GPL.
I've long since settled on WikidPad, but very recently have started thinking of TomBoy -- JaysenNaidooWikidPad is free at the moment. There is a link on their site. -- JRoeterd
Yes. Happily, Jason Horman released WikidPad it under his own open source license, similar to BSD license, in June 2005 -- JaysenNaidoo