In case anyone's looking for a Siri port for their old phone,
watch out for fakes and scams that will try to steal your privacy and infest you with malware.

To date (10/26/2011) there is no "real" port available, only scams.
It is impossible to get Siri for an iPhone 2g, 3g, 3gs, 4, an iPod 2g, 3g, 4g, or iPad 1g or 2g.
(if this should change, you will see news articles posted by reputable authors on MMi, cnet, wired, etc.)
Wait for confirmation. If you can't wait, and you run across a site named something like
"1ams1r1 dot com" or posted with something like this thread's subject line,

Don't bother. fake/scam/fail
Sorry, but that's the breaks.

Siri was made for iPhone 4s, not u.