TiddlyWiki - a non-linear personal web notebook
DokuWiki - DokuWiki is a simple to use and highly versatile Open Source wiki software that doesn't require a database.
Scribbleton - The little personal wiki.
Zim Wiki - Zim is a graphical text editor used to maintain a collection of wiki pages. Each page can contain links to other pages, simple formatting and images.
Pepperminty Wiki - An entire wiki in a single PHP file. Intended for small - medium sized wikis.
wikidPad - wikidPad is an application for storing thoughts, ideas, todo lists, contacts, or anything else that user can think of to write down.