gestikk provides mouse gestures for you, supporting many linux window managers. With gestikk, you can easily control your PC by drawing gestures with the mouse: mouse gestures. Gestikk allows to define an infinite number of gestures, which start applications or simulate key presses. Versions >= 0.5 uses PyGTK for GUI and python-virtkey for keypresses.
Handwriting recognition, like its cousins speech recognition and optical character recognition, is a domain still dominated by proprietary products. Where there are Linux solutions, such as the one in Nokia's Maemo Internet tablets, they are often closed source plugins protected by patent claims. Thus I was pleasantly surprised to find CellWriter, a small, straightforward handwriting recognition tool that integrates easily with modern Linux desktops.