Best Buy published a section on their mobile site saying that the "Pure Google" Nexus S is available only at Best Buy this holiday season. A link to pre-order it doesn't work, and there's a bad image with the alternate text field showing "Nexus S for T-Mobile."
Besides the name Nexus S, little is known about the device. While hints have suggested that it'll be a Samsung based device, there's still no definitive answer and Google hasn't even admitted that the device exists.
Engadget spotted the picture below hidden deep within the mobile site and it looks a lot Galaxy S, running stock Android (possibly 2.3, based on the green icons and black notifications bar) and harboring what looks to be a front facing camera.