Pay close attention to Discourse and Moot.
Both are simple, clean, lightweight, well-integrated, upgrades on traditional forum-technology.
Both prove that organizations don’t have to spend their community budget on their platform.
Discourse is open-source, developing fast, and technically superior. Moot is embeddable, flexible and easier to use.
They might just be what organizations struggling to pay for community platforms need right now.
See http://bbs.boingboing.net/ (Discourse) and https://moot.it/forum/ (Moot).