Found this on some board only I can't remember who deserves the credit - it was however given freely for those who have PHP installed. You just write it up in a text file save it as say, galleries.php and stick it in the same directory as your gallery list.
<?
$f = file('galleries.txt');
srand((double)microtime()*1000000);
$num = rand(0,count($f)-1);
$url = $f[$num];
header("Location: $url");
?>
Hope it helps
