Recently, I had to shut my forums down for a month or so (cause I had seriously screwed my code). When I finally got them lively up again, I had this idea for the email list section of the Admin pages which would have been so sweet.
A textarea at the bottom of the page could hold a message (perhaps a mini-newsletter or announcement) Next to each email address might be a checkbox, and at the top a couple of buttons for check all / clear all etc. When I want all my members to know about something I click check all at the top, then fill in my message and click send. I'm asked again to make sure I'm the admin, then all the checked email address get the message.
Would have been so cool to fire out an email announcement to all my current members, that my forums are alive again as easily as that!
I'd have a go myself but I'm lining up for the big 3.4 upgrade next.
I used to have this email mod but when you have thousands of members it's an absolute pain in the neck to use. Sending the message to more than 50 people at a time nearly always caused a timeout.
If I want to send a message to all of my members I just use the feature available to admins in the PM mod - "PM All Users". Most users enable PMs and have PM email notification switched on so they'll get the message.