Seen in the headers of EVERY message to ruby-talk:

List-Unsubscribe: <mailto:ruby-talk-ctl / ruby-lang.org?body=unsubscribe>

Ryan

On 6/1/06, Travis Detert <travis / gsdesign.com> wrote:
> Sorry to send to the whole group, but I subscribed ages ago, and I've
> completely forgotten where to unsubscribe from the list!
> Thanks!