TinyMCE - TinyMCE is a content editor that functions as a plug-in for Wordpress websites.
FreeTextBox - FreeTextBox is the most-used free ASP.NET WYSIWYG HTML editor featured in open source and commercial projects.
FirstPage - First Page is a free web builder to design and manage the professional level of websites as you want.
Froala Editor V2 - A beautiful modern WYSIWYG HTML text editor
TextControl - Text Control Reporting combines the power of a reporting tool and an easy-to-use WYSIWYG word processor embeddable in .NET applications.
Edtr.io - Intuitive WYSIWYG web editor, open source & fully adaptable.