It's not free, but this forum uses
http://www.vbulletin.com/
Have a look at
http://www.phpbb.com/ for a free forum solution though. As long as you have some webspace that allows you to use your own PHP scripts, then you can use either of the above.
Also, check what your webhost provides. Some have forum software available as part of their packages.
Note: Virgin, AFAIK, don't support any scripts on your webspace, and don't provide forum software.