Here are two interesting rich text editors I've found over the past few weeks:
HTML Edit Box 2.0
This one only works with IE, but its pretty cheap ($40), and its pretty nice. The way it works is kind of interesting, the editor does not get embedded into your web application, it runs as an independent service. You simply put a textarea and a button or link on your page that uses some javascript to open the editor in a new window. When you click the editors "Save" button, it places the HTML code inside the textarea on the calling page. OH ya.....the service needs PHP to run, and that may be a problem for some folks.
There there is this guy
DotNetEdit
This is a control, only works with IE and its got a bigger price tag..but its not a bad editor. It comes with instructions how you can replace FTB in DNN if you want to do that...or you can create a new module that uses it.
I kind of like the HTML Edit Box 2.0 approach, because the editing takes place outside of your web application, and you can easily make the editor of your choice work this way too.