We wrote this, but it really doesn't scale well up to hundreds of links (would work, but a pain in the ass).
Code:
<?
switch($HomePageHits%3) {
case 0:
print <<<ENDBANNER
<a href="http://firstlinkhere.com" target="_blank">Link 1</a>
ENDBANNER;
break;
case 1:
print <<<ENDBANNER
<a href="http://secondlinkhere.com" target="_blank">Link 2</a>
ENDBANNER;
break;
case 2:
print <<<ENDBANNER
<a href="http://thirdlinkhere.com" target="_blank">Link 3</a>
ENDBANNER;
break;
}
?>
If you decide to use it, let me know if you have any questions about how it works.
Edit: $HomePageHits needs to be an incrementing number. In our case we use the counter for home page hits from our db.