I wrote a script to send random daily/weekly/monthly photos and articles automatically. You can have users manage their own subscription through a web interface or just through email, or administer it yourself manually. All of this is completely free and open source.

Here's a detailed how-to:

http://www.examiner.com/x-8158-Open-Source-Examiner~y2009m9d21-Set-up-your-own-mailing-list-manager-send-automatic-dailyweekly-emails-using-ZenPhoto-and-Mailman

I can't test it myself because I don't have SSH (you probably could mention that Mailman is a Pyhton script) but we of course added it to our extensions page:
http://www.zenphoto.org/2008/01/hacks/#mailman

I also wrote a small news post: http://www.zenphoto.org/2009/09/third-party-mailing-list-manager-with-zenphoto-and-mailman/