I have a use case that Drupal doesn't handle very well out of the box. It's funny, as you'd think it would be something everyone would want and, as such, there would be a stronger contribution in the core. The use case is this:
"Site administrator can filter site users by any available criteria and contact them via email as well as save them as mailing groups."
I've been researching the various modules contributed for user contact and the smartest one I've found (and indeed, the only one which sounds like it will robustly meet my client's requirements) seems to be Views Mail: http://drupal.org/project/views_mail
I haven't actually installed this module yet, so perhaps this blog is premature, but if it does what it says on the tin then I think it's a pretty powerful option. The developer, Ron Parker [new window] was smart enough to realise the Views module can already do, combined with Usernode/the User module, most of the sorting labour for you. So no writing complex SQL queries etc.
All he needed to do was create a mechanism for contacting by email the authors of the nodes in a given View. Then he could create groups of users by building and saving Views, which he could then email at his leisure. Very cool and harnessing a lot of hard work other folk have already put in. I like his style!
I will let you know if it works as well as it sounds like it will.