For editing my Hindi words list, I use open-source texteditor Yudit. Though a plain, Spartan, interface, it does the job of typing Devanagari text.
Yudit was installed using MacPorts.
2011 Update
Compile Yudit from source. Source downloaded from www.yudit.org
$ cd /opt/local # use Macports' location $ sudo curl -O http://www.yudit.org/download/yudit-2.9.6.tar.gz $ sudo tar xvzf yudit-2.9.6.tar.gz $ cd yudit-2.9.6 $ sudo ./configure prefix=/opt/local/bin $ sudo make && sudo make install |