Adam Frame released an integration for the famous html-editor Spaw today. It's a little bit tricky to install, but it works really great. You can grab it from the filebase.

Spaw is a textarea editor which doesn't open in a new window like the Mambo html-editor. It's like the well known HtmlArea editor, but it is fully gpl.

Note: I updated the version in the filebase. The old one had a little bug...