Zim aims to bring the concept of a wiki to your desktop. Every page is saved as a text file with wiki markup. Pages can contain links to other pages, and are saved automatically. Creating a new page is as easy as linking to a non-existing page. This tool is intended to keep track of TODO lists or to serve as a personal scratch book. But it will also serve you when writing longer and more complicated documents.

http://dl.openhandhelds.org/cgi-bin/pandora.cgi?0,0,0,0,8,337