Greasemonkey Script - Chat Notifier
Chat has been particularly active lately, and I was inspired to re-try making a script to beep whenever someone posts in chat. I often have Metroplexity open in a back window and then either forget I'm logged in or don't check often enough to see new messages.
http://metroplexity.wikidot.com/local--files/greasemonkey-scripts/chatbeeper.user.js
I've found it super useful over the past few days. Edit the first line of the script if you don't want it to beep at you more than ever x minutes. Let me know if any problems.