I looked for a version of Composer for OS X, and it doesn't seem to exist. Composer was a part of Communicator 4, but recent versions don't have it.
I haven't tried OpenOffice yet (big download) but if it has a WYSIWYG HTML editor, I might just try it. Amaya's okay, but it has a beta feel to it. (Well, more like an alpha with a clunky interface...)