This addon will play a sound (your choice) when a channel (your choice) gets a new message, i.e. never miss a guild message, or party, or raid, or even general channel message. The sound files are kept in the shared media.
Chat Watch was written waaaaay back near the beginning of WoW's release. I have no idea who the original author was, but I have used this through many years of playing. Now, with Cataclysm, some changes needed to be made -- so I made them. Others that might've been reliant on this addon will still be able to use it. Just make sure you delete the old savedvariables .lua files, since this version (8.3) is the first to use a configuration file & shared media sound).