Arnold Jagt has written up a how-to for getting the popular FCKEditor to work with ExpressionEngine. This will basically allow you to switch to a WYSIWYG editor for entering posts into ExpressionEngine merely by double clicking on the textarea field you want to use it on. Implementation will require the hacking of a couple of source files, but if you’ve been looking for a solution like this the changes required appear to be rather minimal and the editor is pretty robust.
Huh. Interesting.
Some instructions for using it with MT are here—I haven’t tried it, but, damn, that looks interesting.
Cool!