Gogh is an extremely lightweight drawing program designed for pressure-sensitive devices. Despite its simplicity, it packs in a lot of features and a lot of fun.
You can download Gogh packages from the project's Web site. The latest release is 0.1.2.1. Gogh is written in Python, and you can uncompress and run the source code tarballs from any place on your system -- no compilation or installation step required. You do need to have PyGTK, PyXML, and gnome-python installed. All are run-of-the-mill Python packages, though, so check your distribution's package management system.
You do not need a pressure-sensitive device like a Wacom tablet to use Gogh, but without one you are far more limited in what you can draw.