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.
wikidPad - wikidPad is an application for storing thoughts, ideas, todo lists, contacts, or anything else that user can think of to write down.
Banana Dance Wiki/CMS - Free open source software combining the best of wiki and CMS with community building-features.
Joplin - Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, tagged and modified either from the applications directly or from your own text editor.
TiddlyWiki - a non-linear personal web notebook
VoodooPad - VoodooPad is a personal wiki developed for the Mac OS. It lets users create a personal wiki by giving them the ability to manage a network of pages right from the desktop.