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.
CellWriter provides a small, grid-like window into which you write with normal pen strokes. Thus it works best with a pen interface, such as a Wacom tablet, but that isn't strictly required.