[Matre]

<select id='cityselect'>
	<option>
		Москва
	</option>
	<option>
		Санкт-Петербург
	</option>
	<option>
		Нижний Новгород
	</option>
	<option>
		Новосибирск
	</option>
	<option>
		Красноярск
	</option>
	<option>
		Хабаровск
	</option>
	<option>
		Хабара
	</option>
</select>

<input type='text' id='cityvalue' />

<script type='text/javascript'>
	var elems = document.getElementById("cityselect").options;
	var similar = function (A, B) {
		for (var i = 0; i < B.length; i++)
			if (A.charAt(i) != B.charAt(i)) break;
		return i;
	};
	document.getElementById("cityvalue").onkeypress = function (event) {
		var max = 0;
		for (var i = 0; i < elems.length; i++) {
			var A = elems[i].innerHTML.replace(/^\s+|\s+$/g, "").toLowerCase(),
			B = (this.value + String.fromCharCode(event.keyCode)).toLowerCase();
			if (similar(A, B) > max)
				elems[i].selected = "selected", max = similar(A, B);
		}
	};
</script>