I have seen praps a dozen or so bulletin board / forum systems, which all look identical in layout and operation. Then only differences appear to be a bit off skinning and css. Some are open source, some are commercial. Some look great, some look terrible... but they are all essentially the same concept.
I'm trying to develop a system which redefines the way a forum should work. I'm basing mine on an infinitely expandable tree of branches and nodes, easily navigable and easy for users to build upon.
TBH, there is a *lot* of work to be done on it, but if you're curious, take a look at http://220.127.116.11/
I would be interested to hear peoples' comments. It's just my evening hobby anyway
It'll never meet the quality of this forum, though (Linuxquestions is just a brilliant site) !!!