Mars Notebook

Mars Notebook is a very useful tree-styled personal information manager. You can use it every day as your assistant in your work and life. It always can be close to you - in system tray and ready to help. It has full featured text editor with tables, any kind of font formatting, colors, bullets, numbering, indents, line spacing, font spacing, undo or redo, spell checker, styles and more. You can print, preview, and edit document properties.

Limitations:

Max 15 sections, no encryption