Can't pick up any hints from the source. My guess is that it is a custom or enterprise solution given the complexity of the site.
It looks a bit like those cNet sites. But I also couldn't find anything that said what it was using. But it shouldn't be that hard to make with the Drupals/Joomlas out there. ~silverwing
It's a custom CMS. There's a small mention of it buried deep within an interview with Tim Weller (CEO of Incisive Media who own vnunet).
Yep, this looks like a custom job. However, others are correct that you can emulate this layout (with a bit of skill) using any of the major Open Source CMS solutions out there. Pick the right combination of templates and plugins (extensions, components, modules, etc.) and you are pretty much on your way. In fact... the layout of the site you've posted is very similar to several high-quality Joomla template club templates I've seen lately, particularly at Joomla Art (no, I'm not an affiliate, just saying that you can pretty much get this look or close to it out of the can ).