random.php
-----------------------------------------------
<?
$delim = "\n";
$cryfile = "galleries.txt";
$fp = fopen($cryfile, "r");
$contents = fread($fp, filesize($cryfile));
$cry_arr = explode($delim,$contents);
fclose($fp);
srand((double)microtime()*1000000);
$cry_index = (rand(1, sizeof($cry_arr)) - 1);
$herecry = $cry_arr[$cry_index];
echo $herecry;
?>
-----------------------------------------------
galleries.txt
-----------------------------------------------
<a href="gallery1.url">Gallery 1 Description</a>
<a href="gallery2.url">Gallery 2 Description</a>
<a href="gallery3.url">Gallery 3 Description</a>
etc...
-----------------------------------------------
Then just call them:
php
<? include ("random.php"); ?>
ssh
<!--#include virtual="random.php"-->
or try
http://www.gallerybooster.com
or see sig for Gallery Admin
Not free, but few great scripts are