Rich Text Editor on CodePlex
This is really great to see. RTEs are a pain to write yourself.
http://ledgards.com/blogs/josh/archive/2007/11/12/rich-text-editor-control-on-codeplex.aspx
My only requests are that they add Opera and Safari support, XHTML support, undo and better flexibility for customizing it (like hiding the view tabs and ASP.NET Themes).
Definitely worth checking out!