auto-completion

Hi,
Does anyone have written something to have auto-completion in ListBoxes?
I.e. having the ability of typing the first letters of your wanted item to navigate in the list
NB: on a traditional listboxes you can only type the first letter.

This can be implemented on the client side only when all the list is downloaded or on client/server mode when the selection is automatically updated by requests to the server (AJAX).

If anyone has already written a solution, could he share it please?

Thank you