Greeklish to Greek Converter (ILSP)
tar jxvf greeklish2greek.tar.bz2
you need pygtk, gtk, libglade and python-libglade and internet connection.
To get all the above (expert from internet connection :P) start from http://pygtk.org/downloads.html
UPDATE: You can also use this web service (limit is 5000 characters which should be enough)