http://code.google.com/p/radiant-fckeditor-extension/
I have been working on this since last night and it is finally
working well enough that I feel comfortable mentioning it. Now you
can use FCKeditor for editing pages. I’ve added it to the Third-Party
Extensions wiki page at the bottom.
I still need to make it a proper text filter since it currently just
clobbers the whole text filtering system for pages. I’d love some
feedback. Once I get it working as a standard text filter I plan to
integrate an asset manager as an additional extension to compliment
it. Eventually I hope to incorporate the configuration into an admin
panel to make it easy to adjust FCKeditor’s various settings.
-James