Batflat - Lightweight, fast, easy, and free CMS.
Adobe Experience Manager - Adobe Experience Manager is a cross-platform CMS that works across websites, mobile apps and on-site displays.
Grav - The modern open source flat-file CMS
Structr - Open-source data CMS platform.
WordPress - WordPress is web software you can use to create a beautiful website or blog. We like to say that WordPress is both free and priceless at the same time.
OnBase - OnBase is an enterprise content management and process management software suite.