plemieux' function did not work for me without passing the encoding to every single mb function (despite ini_set('default_charset', 'utf-8') at the top of the script). This is the example that works in my application (PHP 4.3):
<?php
function my_mb_ucfirst($str, $e='utf-8') {
$fc = mb_strtoupper(mb_substr($str, 0, 1, $e), $e);
return $fc.mb_substr($str, 1, mb_strlen($str, $e), $e);
}
?>