Well, you could have a web interface where people posting there have the message sent out to all users via bcc and with the website's email as the sender/receiver (thus hiding the list of people). I'd almost consider that the poor man's list. This is sorta what MSN does/did for their groups/lists.

I could imagine it in PHP fairly easily. Just do an interface to input the message, instead of posting it to the web, send it to database (for archives) and then have it use the mail() to forward it to users. You'd need some taint checks and such, make the emails plain rather than HTML based (HTML based emails tend to have hidden nasties in them). Shouldn't be that hard to make. I suppose you could do it in Perl (not my fav web language).