The site's up for Grand Theft Auto Chicago, due to hit the Playstation 3 exclusively in October 2007.

Shocker! Or perhaps April Fools joke is more likely. When did Rockstar ever do a real city?

Update

I just heard back from Rockstar. I asked them if the site was for real or a joke or perhaps a bit o fan fiction. Their reply:

"This is not a R* site, and as such, is a hoax."

GTA Chicago [Rockstar]