[Cyricx]

VBAdvanced will solve your needs

From there you can use an htaccess file to redirect from that domain to a several different pages.

However.... the sites must keep uniformity and must be obviously part of the same whole site otherwise you'll come dangerously close and perhaps cross the user agreement with vbulletin.

Here is my site for example.

www.mmogcommunities.com

from the mainpage you can see the various other mainpages. Like the mpsquad site www.mmogcommunities.com/index.php?page=mpsquad

You can easily setup an htaccess file to redirect like www.mpsquad.com to that new url.

Though right now the mpsquad chumps have an entrance page hosted elsewhere with a link to that url, but you get the point