Hoople - 4:00 pm on Oct 10, 2013 (gmt 0)
There are a number of small IRC chat room servers that offer an AJAX front end. Many allow you to hide the room (+secret). I found one very friendly server that I've used off and on. I don't have the URL handy, which is prolly good as the mods will sweep it away...
There are a lot of java based webpage add-ins that link to chat servers. They have two downfalling:
1) user must install full java.
2) All free/low cost ones enclose the chat window in a multi tile ad display.