Ping! is a simple mod that, when installed, will alert the user when they are mentioned in chat. This was created based on this feature in many IRC clients. It has a few default sounds, which can be changed in the configuration file "config/ping.cfg".
Information here is not up to date. Please see the wiki, because I can't be bothered to update the information in 6 different locations.
(Side note: "(Chat)" is only in the name due to the already existing "Ping" mod by dmillerw; this mod is just called "Ping!")