I use an ASP/Javascript editor for my clients that works in IE, FF, and I believe NS (haven't tried the new version on NS yet), and it's almost idiot-proof.
http://www.innovastudio.com
I say almost because one of my clients has figured out that you can't code a page to stream a video since it doesn't support ASX files.
Also, if users copy/paste from Word without using the Paste from Word button, they'll get the code that Microsoft generates when it converts a Word doc to a web page. (This is the biggest weakness I've found with the product to date, but the button serves as a workaround and if people copy/paste to Notepad and then copy/paste to the editor, Notepad strips out the formatting.)
However, the positives of the tool far outweigh the negatives. It functions very similarly to Word, which I would say most people are at least familiar with; the adding/deleting/modifying of pics and pages using the Asset Manager is an excellent feature; if you want to, you can even control what can be uploaded.
And most importantly, it's very WYSIWYG. So it's very easy to use.
Note: I'm not a reseller or anything and I never built the tool. I'm just a customer that likes it.