[ Thanks to Linuxaria for this link. ]
Sometimes we want our Linux box to speak to/for us.This
ability is very useful to make announcements and alerts in case of
many critical events in our machines or can be used just for sheer
fun. There exists a command line synthesized known as eSpeak that
comes pre installed in Ubuntu.You can also install it on debian systems by typing the command
sudo apt-get install espeak in a command console .For all other
operating systems you can install it from source available at
http://espeak.sourceforge.net/download.html