A simple test for the Wacom web plugin. Docs are here and here. See also a basic test application, a scribble example), and a more advanced demo example.
Wacom tablets are interesting input devices: they provide sub-pixel resolution input (more precise than screen pixels), information about the stylus pressure, proximity data (the pen is sensed even if it does not touch the screen) and device identification (e.g. pen tip vs. eraser tip).
Unfortunately, in order to receive such data from a Web application, a plugin needs to be installed (download from here if you feel lost in the messy Wacom website). You also need a Wacom driver for your tablet, not the one Windows installs automatically (I