Please check this example: 

http://richtexteditor.com/test/property/allowscriptcode.aspx

Here is the setting of this editor:

<RTE:Editor ID="Editor1" AllowScriptCode="true" TagBlackList="" runat="server" /> 

asp.net Chat http://cutesoft.net/ASP.NET+Chat/default.aspx
Web Messenger: http://cutesoft.net/Web-Messenger/default.aspx
asp.net wysiwyg editor: http://cutesoft.net/ASP.NET+WYSIWYG+Editor/default.aspx
asp wysiwyg html editor: http://cutesoft.net/ASP
asp.net Image Gallery: http://cutesoft.net/ASP.NET+Image+Gallery/default.aspx
Live Support: http://cutesoft.net/live-support/default.aspx