The multi-purpose note-taking application for KDE. (GPL)

A hierarchical note taking application, featuring rich text and syntax highlighting. (GPL)

Day Planner is a program designed to help you easily plan and manage your time. (GPL)

The main objective of Getting Things Gnome! is to provide a simple, powerful and flexible organization tool to the GNOME desktop environment. (GPL)

Gnote is a port of Tomboy to C++. It is the same note taking application, including most of the add-ins (more are to come). (GPL)

GTT is a to-do list/diary/journal tool that can track the amount of time spent on projects, and, among other things, generate reports and invoices based on that time. (GPL)

Incollector is an application to collect various kinds of information (like notes, conversation logs, quotes, serial numbers, source code, web addresses, words). (GPL)

Jarnal is an open-source application for notetaking, sketching. (GPL)

With KeepNote, you can store your notes in a simple notebook hierarchy with rich-text formatting, images, and more. (GPL)

Lifeograph is an off-line and private journal and note taking application for one's self evaluation of his/her own life. (GPL)

NoteCase is a hierarchical note manager (aka. outliner). (BSD)

Osmo is a handy personal organizer, which includes calendar, tasks manager and address book modules. (GPL)

qOrganizer is a general organizer that includes a calendar with schedule, reminders, journal/notes for every day, to-do list. (GPL)

Referencer is a Gnome application to organise documents or references, and ultimately generate a BibTeX bibliography file. (GPL)

Task Coach is a simple open source todo manager to manage personal tasks and todo lists. (GPL)

Tasque is a simple task management app (TODO list) for the Linux Desktop. (GPL)

Tomboy is a desktop note-taking application for Linux and Unix (GPL)

Wixi is a multi-platform wiki application for the desktop. (GPL)

Xournal is a GTK+/Gnome application for notetaking, sketching, keeping a journal using a stylus on Tablet PCs and other platforms. (GPL)

Zim is a WYSIWYG text editor written in Gtk2-Perl which aims to bring the concept of a wiki to your desktop. (GPL)