http://www.rockstargames.com/IV/ I just started looking through it and the first thing I saw was their parody of Sprite (Sprunk) and their hip hop marketing campaign (We even sponsored that movie, "Popping!"). Lots of stuff to waste time with.
PSM3 had a preview of GTA4. Some scans can be found here: http://www.gtaforums.com/index.php?showtopic=311011 Too lazy to read through it myself right now, but I think these are some highlights of the scans (taken from Loudninja at NeoGAF): BTW, I think sites like Gametrailers and Gamersyde have the screens and/or videos from the website, so you can check those out if you can't access the site. Of course, you miss out on a bunch of other stuff too.