A few weeks ago, both Marc Liyanage and John Gruber explored the Applescript Reference to a Uri for emails from Mail.app.
http://www.entropy.ch/blog/Mac+OS+X/2007/12/04/Copy-Message-URLs-AppleScript-for-Apple-Mail.html
http://daringfireball.net/2007/12/message_urls_leopard_mail
It could be really nice to be able to have the message:// protocol registered in Terminal or iTerm, so that command+double-click on the url/uri would do just the same as on a http:// link: open it. I used their scripts in combination with Act-On which let’s me now press a command $ then U to copy the Uri of the selected email to the clipboard (Basically: Act-On replace the clicks on the Applescript menu from Applemail by shortcuts). It would be nice to be able to log directly in todo.txt the email Uri fr later retrieval/processing.
todo.txt: http://todotxt.com/
act-on: http://www.indev.ca/MailActOn.html