statuspage - A simple self-hosted status page site with an API written in Django under the BSD license.
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
YUNO - YUNO is a web data driven company focussed on solving customer challenges in web data discovery and extraction space.
Zoho Desk - Industry's first context-aware Helpdesk Software
FreshStatus - Better status pages in 1-click, FREE FOREVER
Salesforce Service Cloud - Service Cloud integrates customer service with social networks and provides a self-service customer portal and knowledge base system.