Today, I've merged my erc notifications module inside Emacs trunk. This way, it will be available for everybody in Emacs 24.2.
This module allows you to be notified via
(the Emacs implementation of the Freedesktop desktop
private message received on IRC, or when your nickname is mentioned on a
To enable it in Emacs > 24.1, you just have to add the following line to your configuration file:
(add-to-list 'erc-modules 'notifications)
If you want to download it and use it stand-alone for a previous Emacs version, you can fetch the latest file revision and load it before adding the previously given line.