Or a server side language.
For example...
PHP:
<?php
$options = array('John', 'Eric', 'Thelma'); // and 97 others
sort($options);
?>
<?php foreach($options as $k=>$v){ ?>
<?php echo $v?>
<?php } ?>
Python:
options = ["John", "Eric", "Thelma"]
options.sort()
# Gives you a sorted list, then do your HTML thing as above
This could be done in javascript, but I wouldn't recommend it. Javascript might be switched off, and if you're injecting 100 elements into the DOM, that would be awfully slow. The best way to do it would be to put all 100 elements into an array, sort it, build the HTML in a string, then inject the string into the select list's innerHTML.
But really, server side is the way to go.