Jordi Cabot

In the Settings->Discussion page, authors of a post can use the checkbox Email me whenever – Anyone posts a comment.
But this does not send an email as well to the site admins. In blogs where you have a number of guest authors, you may want to be informed about all the new comments so you can respond (if the author is missing) or just participate in the discussion.
As a site admin myself, I was missing many comments. This means plenty of missing opportunities to engage with your audience.
To solve this situation, the plugin adds a new checkbox in the Discussion page. If checked, admins will get an alert email for new comments.

Comment Admin Notifier

Very simple plugin that doesn't try to do many things. But the one it does is very useful: as a website owner you want to make sure you're on top of all the comments in the site even comments to posts you didn't write. 

It does one thing and it does it right

With this plugin, admin users get an email alert every time a new comment is posted on ANY post in the site.

aleapp

WP Cookies Alert allows to display an alert box on your WordPress blog notifying visitors you blog uses cookies as EU Cookie Law requires. 
You can display a short message or publish a link to a page with extended explenation. 
WP Cookies Alert works in multilingual blogs and can be translated to multiple languages. English and spanish are included.

WP Cookies Alert

This plugin adds an alert box notifying visitors your blog uses cookies.

Comment Admin Notifier vs WP Cookies Alert