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. Pages are stored in a folder structure, like in an outliner, and can have attachments. Creating a new page is as easy as linking to a nonexistent page. All data is stored in plain text files with wiki formatting. Various plugins provide additional functionality, like a task list manager, an equation editor, a tray icon, and support for version control. Zim can be used to keep an archive of notes, take notes during meetings or lectures, organize task lists, draft blog entries and email, or do brainstorming.
libktomgirl is a library that reads a subset of the Tomboy file format. When it's done, it should support reading and writing all aspects of files created by Tomboy, Gnote, and KTomGirl. Despite the K in its name, there are no KDE or Qt dependencies (nor C#, GKT, or GLIB). This is pure C++ with boost and stdlib only. Most of the code is from Gnote.
SourceNote is a program for taking notes. It lets you add text, pictures, and your own drawings, all of which are packed into different boxes which you can move around, making organization easier. The interaction is optimized so that you can switch easily between your opened tabs, as in a browser.
Textportal is a simple script which can be used for a variety of purposes. Put it in a password-protected directory on your site, and it can be used for keeping a private notebook or diary. On a public page, you can use it as a simple chat or shoutbox script, or for sharing images and links.