[tormodg]

I am not aware of any such mod, but the vB templating system certainly makes it possible to do. We are working on something similar for our portal, but we don't have "multiple joomla installations" but a custom-built portal system which will incorporate forums for different users in different topics.

It's not really that hard as long as you can use one userbase and can get a programmer who understands vB's templating system.

There are earlier posts on "multiple forums with single userbase" somewhere around vB.org but they often come down to the technical challenge that arises when people sign up (ie if the forums each have a completely different look and feel, it gets confusing). If you however intend to have one name for your entire website, even if each subsection has a different focus it should be clear to the user where they have registered (ala Gamespot as you mention - the user's don't worry about signing up for Xbox 360 forums, they're happy to be Gamespot members).

I'm however not the person who can help you since I am basically a web editor who gets technical help from others so I'm still looking for good examples of sites that do this.