I created an autoresponder / subscription-confirmation script. It is currently successfully in use on a client's site. If anyone is interested in purchasing this script, please contact me for details.
Michael, sounds very cool. Any chance you can share a little more about how the script might work so you can give those interested a better idea of what to expect?
The form where the subscriber enters their information now gets submitted to a local url (in this case a php file, though it could have been Ruby, etc.) instead of a CM one. The script does some basic validation on the form data, subscribes the given email address via the CM API, sends a custom confirmation email to the subscriber and another custom email to the site owner. If an invalid email address was provided or the CM API call was not successful, an html error page is displayed. If everything was successful, an html "thank you" page is displayed (which can use fields from the submitted form. e.g. "Thank you <Name>").