Reference

http://web.appstorm.net/roundups/40-fantastic-self-hosted-business-apps/                                
http://www.opensourcecms.com/scripts/show.php?catid=4&category=Groupware                                
http://www.cmswire.com/cms/social-business/why-these-6-enterprise-social...                                
http://www.cmswire.com/cms/enterprise-cms/exo-platform-an-open-source-en...                                
http://www.gartner.com/technology/reprints.do?id=1-1K6VW2C&ct=130913&st=sb

Comparison (by Michael Bakonyi, to be corrected)

TypMaintainanceExtendableOpen SourceCommunity-drivenUsabilityFunktionsumfang
ExoColab++++?++
Mindquarry?– –?+++?
Concrete5CMS++???+
CollabtiveColab++?++?++
Feng officeColab+++++– –++
GroupOfficeColab++??– –+
Liferay+++++++
Microsoft SharePoint ServerColab++?– –??
OpenERPColab++?++?+
Open AtriumColab+ +++ +++
OpenText ECM SuiteCMS--
OpenProjectTicket++++++++++
Oracle BeehiveColab++?– –– –
PimcoreCMS++???
Red Hat JBoss MiddlewareColab++?++??
RedaxscriptCMS++?+
SocialcastColab?????
TeamLabColab++??– –++
TineColab??++++-
TikiwikiWiki++++++– –
WebCollabColab++?+++++
ZarafaColab++– –-