I'm using this: http://www.axelscript.com/2008/04/02/introducing-acjeditor-its-a-rte/
Check it out.... it should get you started... i'm using it, i'm in the middle of the project and havent ran it through any validators, but it sure is a lot better than flex's RTE... i had to actually just totally copy and paste the RTE into my own and open up some of the methods... my email is jensen.axel (at) yahoo.com let me know if you have any questions...
