I apologize if this question is vague, but I want to build a drop down header, very similar to the one on StackOverflow that alerts you whenever you have earned a new badge, or on Twitter whenever a new tweet comes in.

I've been looking around on the internet for a tutorial, but I'm having trouble googling exactly what I'm looking for. I assume there is a way to do this in jQuery, or there may be a jQuery plugin for it, but I haven't had any luck finding one.

The idea would probably be to make an AJAX request every so many seconds, and if a new alert-worthy item is found, display it for the user.

If someone could point me to a resource to learn how to build one, and/or an existing plugin, that would be great.