Meta Box Datepicker

public function meta_box_1($post){
// Enqueue Datepicker + jQuery UI CSS
wp_enqueue_script('jquery-ui-datepicker');
wp_enqueue_style('jquery-ui-style','http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.1/themes/smoothness/jquery-ui.css',true);

//This is where the normal meta box stuff goes. Nonce, get_post_meta, etc

?>
<script type="text/javascript">jQuery(document).ready(function(){ jQuery('#presentation_date').datepicker({dateFormat : 'mm/dd/yy'}); });</script>
<?php
}

Easy Form Validation

$(document).ready(function(){
$("#registerForm").validate({
invalidHandler: function(form, validator) {
var errors = validator.numberOfInvalids();
if (errors) {
var message = errors == 1
? 'You missed 1 field. It has been highlighted in red'
: 'You missed ' + errors + ' fields. They have been highlighted';
$("div.error span").html(message);
$("div.error").show();
} else {
$("div.error").hide();
}
}
});
});

AJAX Refreshing DIV

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>

<script type="text/javascript">
$(document).ready(function() {
$.ajaxSetup({ cache: false }); // This part addresses an IE bug. without it, IE will only load the first number and will never refresh
setInterval(function() {
$('#divToRefresh').load('/path/to/your/php/file/userCount.php');
}, 3000); // the "3000" here refers to the time to refresh the div. it is in milliseconds.
});
</script>

<?php
require "/path/to/your/database/connection/connection.php";
$userCount = mysql_query( "SELECT * FROM users" ) or die("SELECT Error: ".mysql_error());
$numRows = mysql_num_rows($userCount);
echo $numRows;
?>

<div id="divToRefresh"></div>