Throbber
I enjoy doing User Interface Oriented Application Development. I normally use throbber in Ajax enabled web application development. Throbber is an animated graphic which is normally used on user interfaces to convey the user that the application is performing an action. On all Apple products it is known as an “activity indicator”.

Throbbers are mostly used in Ajax enabled applications because these applications retrieve data from the server asynchronously in the background without interfering with the display and behavior of the existing page. So its important to convey the user that the application is performing an action.
There is an online throbber generator web 2.0 service at http://www.ajaxload.info/

There is also one Jquery plugin for this http://www.systemantics.net/en/throbber