Sending username / password back to the user

I have a private blog that requires a login and password. With each post, i would like to notify each of my users with an email notifying them tgat there is a new post. Underneath the message, i would like to include their username and password (in case they have forgotten in).

Is there a script any way to display it in an email? I’m assuming i would have to use the email notification plugin (or something similar), but i’m not sure if there are any tags for username/pass that wordpress would recognize?