I am unsure of what exactly your saying,
If they have taken the page source and posted it to domains out of your control I am unsure if there is much that you can do about it.
If they are on domains that you own or have access to then the easiest way is with a redirect. However that answer is too easy to I will assume you don't have control over it.
If it is a case of someone illegally copying or mirroring your site, check out this link which seems to have your first steps on how to deal with the person.
You can inform the major search engines about this, and they will usually be able to tell by the age of the site (and how far back they have you indexed) that you are telling the truth.
The best thing to do is get all of your documentation ready and confront the individuals if you can, and/or their ISPS
Good Luck and I hope this helps.
[edit]
I found this script on another help site, I am unsure of this works:
<script language="JavaScript">
<!---
var Good01 = "www.yoursite.com"
var GoodIP = "123.123.123.123"
var ThisHostName = document.location.hostname.toLowerCase()
if ( ThisHostName != Good01 && ThisHostName != GoodIP) {
alert("THIS IS NOT AN OFFICIAL... SITE");
windows.location="http://www.yoursite.com";
}
// -->
</script>
- I am not the author of this code and can not verify the validity however it seems plausible.
This was used due to the fact that a company was using a proxy method of mirroring the site. (some do this to inject ads before the people get to your real content, and various other reasons).
The original author also noted using ProxyPassReverse (apache directives) to combat server side redirects.
