<p>There are tons of free wysiwyg editors you can embed in web pages. I'm looking for something that is easiest to embed into an adobe air app. Means something that works in webkit and is easy to get the content from with javascript.</p>

TinyMCE
is nice. It's quite popular, even used with the
Symfony PHP framework
. Not sure how it will work out with AIR, but chances are really good. Works with Chrome & Safari like a charm.
EDIT: ... and there's also a
lightweight jQuery editor plug-in
. And the
wmd editor from Attacklab
(WYSIWYM) that is used here, on StackOverflow.