[eluser]Jelmer[/eluser]
I've used tinyMCE for ages, it's not perfect but it does the job quite adequite.
As for a tutorial, what kind of tutorial do you need? In the end CI doesn't really care what kind of front-end you're using. tinyMCE just replaced a textfield, but it's still posted to CI like the output of a textfield. Unless of course you need Ajax like features, but then you'll need to specify a bit better what kind of tutorial you want. (though this question has been asked before, you might find something by searching the forums for "tinymce")
The other big alternative is CKeditor, but I haven't used that or it's predesessor (FCKeditor) for ages. So I can't help you there.
