WoltLab Suite
Discourse
phpBB
Flarum
XenForo
Invision Community
MyBB
Lefora Free Forum
idea.informer
GetSatisfaction
UseResponse
UserVoice
UserEcho
SurveyLab
Zendesk
Trengo
WoltLab Suite idea.informerI really like WoltLab, they have a great Forum and the community is generally really nice The customer support is also awesome
Discourse - Discourse is an open source discussion platform built for the next decade of the Internet.
GetSatisfaction - Get Satisfaction is the leading customer engagement platform that helps companies build better relationships with their customers and prospects, through the best online customer community.
phpBB - Raspberry Pi. The Raspberry Pi is a cheap, credit-card sized computer. The official website uses phpBB for their discussion forums. phpBB is not affiliated with nor responsible for any of the sites listed on the showcase.
UseResponse - Open-source, self-hosted customer feedback software, live chat and helpdesk system that you can install on your server. Organize documentation using knowledge base and get feedback from social networks with centralized system
Flarum - Flarum is the next-generation forum software that makes online discussion fun. It's simple, fast, and free.
UserVoice - UserVoice integrates easy-to-use feedback, helpdesk, and knowledge base management tools in one platform that empowers users to speak and companies to understand.