So we have some interesting messaging code now in Slash. You can get messages for various kinds of events. Someone replies to your comment, moderates it, posts a new journal entry, etc. and you can get a message, delivered in various ways.
[As a quick side note: the code never was rewritten from when it was first written, and it probably should be. Bleah.]
So now I am working on extending it further. You can choose a different delivery method for each kind of message (currently e-mail, web, or none). Soon you'll be able to get the daily headlines / newsletter customized to your personal preferences (don't like JonKatz stories? no problem!). Also in progress is Jabber support, so you can get instant messages sent to you. I am not sure how much I like the idea, but I think a lot of other people will like it, which is good enough.