Wiki on a Stick - Self-contained desktop 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.
TiddlyWiki - a non-linear personal web notebook
ConnectedText - ConnectedText is a powerful but simple information management system.
ZuluPad - ZuluPad is a notepad on crack.
Torchpad - Wiki farm with markdown based wikis.