Tomoe is a handwriting recognition engine for Japanese Kanji and Chinese Hanzi. It is written in C for the Gtk library and includes Ruby and Python bindings.

Mayor Linux distributions currently seem not to ship any packages so building your own packages is the only way to do it. Debian Etch Installation & Configuration is a nice article about how to install Tomoe on Debian. I changed the last step though to use checkinstall which gives you a Debian package allowing for easy deinstalling. I included Python bindings (no Ruby though), excluded the Unihan database and configured Tomoe to create the documentation in HTML though the install process does not include them currently.

./autogen.sh
./configure --enable-gtk-doc --disable-unihan
checkinstall -D make install

I'll upload the .deb package here but first of all it doesn't state the dependencies and secondly you are advised to build the package yourself using the steps mentioned in the link and above.

Update: You can now use Tegaki, the successor of Tomoe, which was introduced into Debian recently.