@TheSiriPort just released their website. Many had hoped that it would be a legit Siri Port, but it turns out that it was nothing but a hoax.
When you open the website, it will guide you through the installation of Siri. But if you take a look at the source code of the website, you will see that it just redirects you to the congratulations page after 15 seconds. So nothing will be installed, you just get to the page that says Siri has been installed successfully.
Maybe @Jackoplane will release his port soon, but it could very well be that he was also pretending to have ported it just to get some attention.
It looks like we just have to wait until the iPhone 4S jailbreak is available.