Per-tag RSS/atom feeds and email subscriptions

This is one of the very few things I miss from WordPress. I could post whatever I wanted, tag it well, and have a little page where I introduced people to RSS and told them how to add a tag's feed to their reader with a handy list of links to each feed. I would also like to see this extended to emails. Right now, email subscriptions are functional but blunt: you get it all as it's posted, or you get nothing.