Confluence is Atlassian's enterprise team knowledge base and document collaboration platform, founded in Sydney, Australia in 2002; with native Jira integration, a free plan for 10 users, and 1,000+ Marketplace apps.
Liferay is an enterprise digital experience platform (DXP) founded in 2004 in Diamond Bar, California, USA. Its open-source community edition is free, and one platform integrates CMS, DAM, Commerce, Search, personalization and AI. Rated 4.6/5.0 on Gartner Peer Insights with a 360+ partner network, it suits large enterprise portals and multisite scenarios.
DNN (DotNetNuke) is an open-source .NET CMS that originated in 2002, deeply integrated with the Microsoft stack, with built-in native multilingual support and granular permissions, plus 1000+ extensions in its marketplace, ideal for enterprise portals and intranets.
Dropbox Business is Dropbox's (founded 2007, San Francisco) enterprise cloud storage and collaboration platform with team folders, 180-day version history, remote wipe, and Dropbox Paper.