Xournal is an application for notetaking, sketching, keeping a journal using a stylus. It is free software (GNU GPL) and runs on Linux (recent distributions) and other GTK+/Gnome platforms. It is similar to Microsoft Windows Journal or to other alternatives such as Jarnal, Gournal, and NoteLab.
You may also want to try out Xournal++ (which started out as a rewrite of Xournal in C++, but now has evolved well beyond the original, while retaining a decent amount of compatibility).
Development snapshots: tar.gz snapshots from the CVS repository or the GIT repository
Previous versions: [0.4.8.2016] [0.4.8] [0.4.7] [0.4.6] [0.4.5] [0.4.2.1] [0.4.2] [0.4.1] [0.4.0.1] [0.4] [0.3.3] [0.3.2] [0.3.1] [0.3] [0.2.2] [0.2.1] [0.2]
Win32 binaries of version 0.4.8.2016 are also available (note the windows version is less thoroughly tested and still unstable).
(You can simply unzip the provided archive into any directory and place a shortcut to xournal.exe on your desktop, but if you feel the need for an installer, you can try this one provided by P.-A. Bandinelli.)
Previous versions: [0.4.8.2016-win32] [0.4.8-win32] [0.4.7-win32] [0.4.5-win32]
Xournal aims to provide superior graphical quality (subpixel resolution) and overall functionality; however it lacks the collaborative features of Jarnal.
Here is a screenshot of the user interface (click to enlarge):
