Using script.aculo.us Ajax.Autocompleter to dynamically search the keyed in values of an input textfield or textarea and provide a drop down selection menu.
The list generated by the component can use either the standard string list, or a more advanced output such as the html that is generated for displaying country flags.
You can very easily enable client-only autocomplete. In this way, all possible values are included in the original html file, and no further (ajax) requests are made. Additionally, tacos will notice if two (or more) autocompleters use the same list source and will optimize the html file size.