changed it to
<select name="sponsorSearch">
<?php do { ?>
<option value="<?php echo $row_Categories['CategoryID']; ?>" selected="selected" <?php if (!(strcmp($row_Categories['CategoryID'], ((isset($_POST["sponsorSearch"]))?$_POST["sponsorSearch"]:"")))) {echo "selected=\"selected\"";} ?>><?php echo $row_Categories['CategoryName']; ?></option>
<?php } while ($row_Categories = mysql_fetch_assoc($Categories)); ?>
</select>
but still not showing the selected filter