I agree with SLaks. You can use an iframe to load sites into your page and control which pages you show. You won't be able to control anything inside of the iframe but you will be able to show it. Also be careful of sites that will bust out of the iframe like stackoverflow.com
Here is an example that I built that I thought would be helpful in illustrating how this can be done. There is lots more that could be added to this to make it really cool, or it can be keept really simple.
Example page => http://mikegrace.s3.amazonaws.com/forums/stack-overflow/example-show-multiple-pages-like-screensaver.html
<html>
<head>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"></script>
<script type="text/javascript" charset="utf-8">
var sites = [
"http://www.thinkgeek.com/",
"http://www.artzstudio.com/2009/04/jquery-performance-rules/",
"http://www.example.com"
];
var currentSite = sites.length;
$(document).ready(function () {
var $iframe = $("iframe").attr("src","http://www.google.com");
setInterval(function() {
(currentSite == 0) ? currentSite = sites.length - 1 : currentSite = currentSite -1;
$iframe.attr("src",sites[currentSite]);
}, 7000);
});
</script>
<style type="text/css" media="screen">
iframe {
height: 100%;
width: 100%;
border: none;
}
</style>
</head>
<body>
<iframe></iframe>
</body>
</html>