Filtering a SELECT group using jQuery
Your jQuery could be somewhat more efficient if you minimize $(...) element look-ups by storing them as variables or chaining them.

Also, I think you will see some benefit to replacing some jQuery constructs with their pure JS alternatives ($.each -> for, etc..)

Check out this set of jsPerf tests from this StackOverflow answer.

&lt;script&gt;
var fullcelllist = $(),
    lastVal ="",
    $celllistOption = $("#celllist option");

// ...

$("#filtercell").keyup(function() {
    var $this = $(this),
        $thisVal = $this.val();

// ...