The CNET forums used to be powered by Jive, but there were too many issues with lacking customizability to fit the growing needs/requests. Thus, CNET undertook a project to create its own forum software, which has been powering the forums for the past year or so. It's all internal - it's not something others could just download and install like phpBB - but I hope others adopt a similar threaded view, which was the design of our forum administrator, Lee Koo. Cheers, Lee!
John
I really like the collapsible threaded view of this forum.
What software powers it?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic