With Mac OS X Panther Apple introduced the new shell command ‘say’ that allows you to directly invoke speech output from the command line.
For example: if you enter the command ‘say Hello’ (without the quotation marks), your Mac says ‘Hello”.
As an alternative the command accepts file input (clear text files only!). An example file can be downloaded here. To listen to a file enter ‘say -f path/filename’.
To make your Mac read the example file copy it to your Desktop, which you have to make your working directory. The whole chain of commands looks like this:
cd ~/Desktop
say -f Welcome.txt
Now your Mac reads out the file Welcome.txt
If you don’t like your Mac’s voice, go to the speech panel in your system preferences and change it till it fits your taste.
What makes this new command very exciting is, that you can use it remotely. Log in to another Mac (ssh username@targetIPadress) and let the remote Mac read your texts. A nice way to call at home 
Please be aware, that you try this tip on your own risk!