Freshdesk - Freshdesk is a cloud-based customer support software that lets you support customers through traditional channels like phone and email, social channels like Facebook and Twitter, and your own branded community
DokuWiki - DokuWiki is a simple to use and highly versatile Open Source wiki software that doesn't require a database.
Zoho Desk - Industry's first context-aware Helpdesk Software
Wiki.js - An open source, modern and powerful wiki app built on Node.js, Git, and Markdown.
Salesforce Service Cloud - Service Cloud integrates customer service with social networks and provides a self-service customer portal and knowledge base system.
TiddlyWiki - a non-linear personal web notebook