Today was looking for a plugin to make huge drop-downs searchable. I have first checked the jQuery Autocomplete plugin, but that works better with plain text inputs, then browsed through tens of other similar plugins and even tried couple of them. Finally, my choice went to jQuery Searchable Drop Down Plugin.
Main reason of choice – ease of setup. Just include the script in the head and then use something like this in your code:
$(function() { $('#myDropDownSelectElementId').searchable(); });
Finish story, works just like it supposed to.