This is a classic AJAX example. Start typing (slowly) one of the words (names) below into the text box. Pressing enter (when no option is selected) adds a new name.
The name list is populated using Reverse AJAX.

The clock below uses Reverse AJAX. Time changes are "observed" on the server and pushed to your browser. If you're using IE6 and hearing a click - that's a side effect of this clock.