Few day ago I was asked to provide assistance to one of my former partner on the Burundi Passport project. He asked about the WYSIWYG HTML editor that he can use with ASP.NET WebForms.
Quite easy, as I just integrated it few weeks ago in on of my products. My recommendation was to use FreeTextBox as it is free, easy to integrate and with decent documentation and users base. The downside is the fact it is not maintained regularly any more.
As they say:
The most-used free ASP.NET WYSIWYG HTML editor featured in open source and commerical projects. Just drop FreeTextbox.dll in your /bin/folder, change <asp:Textbox /> to <FTB:FreeTextbox />, and you're done.