There are plenty of opensource Forum software (web applications) in the market. To me, a better and straightforward community based website can be built through such forum software. I use SMF and MYBB extensively eventhough there are plenty of options available. Xenforo, Vbulletin, etc. are good paid versions but SMF and MYBB can be used a very good alternatives if you can setup the site yourself.
My all time favorite free forum software had always been MYBB due to following reasons.
|In-line post image||No||Yes||MYBB. It is really useful to write better posts.|
|Separate Calendars for different purpose||No||Yes||MYBB|
|Archive Mode Theme||No (plugin available)||Yes||MYBB|
|Portal Integration||SMF with Simpleportal or Tinyportal||In-build portal but not as greats as SMF||SMF|
|Template Modification from backend||Difficult||Easy||MYBB|
|Sidebars option||Various through portal plugin||Limited through advanced sidebox plugin||SMF|
|Plugin Installation ease||One click install||One click install through a separate plugin||SMF|
|Statistics||Many options||Limited options||SMF|
|Help Section editable||No. Only through FTP||Yes. Through backend.||MYBB|
|SEO Plugin||Pretty URLs||Google SEO||SMF|