Ability to create 'sections' in a forum

[lucky64]

I wasn't sure what to search under, so I'll try and describe this instead.

I was wondering if it were possible to create a hack (or perhaps one exists) that gives users the ability to create a thread, and that post begins a new 'section' of the forums in which users can post new threads.

Ok, that sounds odd, let me try an example.

User enters the Lounge, User creates a new topic called Cars. The topic then allows people to make new threads within the topic that appear below it, sort of like little subthreads...with a little indent or small border around the whole 'section'.

I hope this makes sense, it would be a really cool hack.

--Lucky