Looking for a Twitter Script that...

when a person downloads something from my site, it tweets a msg on their twitter account with my link something like: "I just downloaded Xrummer from www.mylink.com"

anyone know of a script that does this in php or anything for that matter?

can it be done?

Yes, you need to make a twitter app and get the surfer to allow access to their account by your app via Oauth.

I don't know of any off the shelf scripts but it can definitely be done. Take a look at tinychat.com for an example.