Batflat - Lightweight, fast, easy, and free CMS.
Laserfiche - Laserfiche offers powerful document management software solutions that are easy to implement and easy to use.
Grav - The modern open source flat-file CMS
DocuWare - DocuWare is a next-gen document management system that is specially designed for transferring paper-based and digital assets into collective resources.
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.
IBM FileNet - Enterprise Content Management platform for large businesses