DHTMLX
  
DHTML eXtensions - professional AJAX components for advanced Web UI.

dhtmlxCombo is a cross-browser JavaScript combobox with autocomplete feature. It extends basic selectbox functionality to meet the requirements of the most up-to-date web applications. dhtmlxCombo can be converted from existing HTML SELECT or populated with JavaScript. Supporting AJAX, it can also get list values from the server datasource dynamically.

Live demo

Editable mode:
Read-only mode:
Filtering mode: (filter existing list)
Autocomplete mode:
(start typing to load convenient country names from server)

Combobox with icons:

dhtmlxCombo can be used in four modes: editable select box – the user can either select a value from the list or type a custom value; read-only select box – the user can select just one value from the associated list of choices; filter – the whole list is loaded on the client-side, and as user begins to type, the list is updated with the appropriate values (which contain or begin from the characters typed); autocomplete – the list is loaded and shown as the user types in the input box.

Like other dhtmlx components, dhtmlxCombo provides complete Javascript API to give developers enough possibilities to control its state and behavior.

Licenses

Open Source - GPL allows using Standard Edition of dhtmlxCombo in GPL projects for free.

Commercial License includes dhtmlxCombo Standard Edition and allows you to use it in one project (application) with unlimited number of copies. According to this license we provide you with support (consultations) and free-of-charge bug fixing during 1 month. This license costs $49.

Enterprise License includes dhtmlxCombo Standard Edition and allows you to use it in unlimited number of projects on condition that all of them are projects of one company. Free support\upgrade period is 12 months. This license costs $99