Okay, it seems I want to get mutt to dance. I've created a snippet of HTML (attached) with a link that's supposed to trigger an email with the body filled out. Mutt respects the To: and Subject: of the mailto: link, but not the option for Body, which is jammed into the Subject: line. The HTML code in question was produced by Bluefish.
-- Humanity's future is in the stars: support a manned mission to Mars! http://www.thinkmars.net/petition/addpetition.html
<a href="mailto:[EMAIL PROTECTED] will trigger the subject header?Body=This is the body of the email. If you can live with it, get real!">Mail trigger</a>