Google Feed Burner
Google feed burner allows you to set up a subcription to your site via email, this could be an RSS feed to your joomla articles so that if you run a blog type site or a site that constantly adds new articles your users can keep up.
Your feed address for your joomla articles might look like this:
After adding this address to google feedburner the result looks like this... click here
Setting up the feed in the module
When you set up a feed burner feed in google you can give it your own feed address.
Now copy the RSS title from google and paste it into the module.
Now with the module enabled users can simply type in their email address and hit subrcribe and google will email them everytime a new article is added to your site.
Other feed services
The great thing about google feed burner is that not only does it email your users, it can also be set up to update your twitter account, going further you can set up your twitter to update your facebook, meaning that you can publish away without every having to think about email, twitter or facebook.
Google Feed Burner 1.0.2