Replying to Subscribe to blog or thread

I've searched and also check site discussion every day and can't remember if this ever came up but on a bunch of other forums there is a feature you can subscribe to a blog (like my threads but without posting in it) or a thread and it will message or email you when someone has posted something in it. I'd rather have a notifier somewhere on the right that says a thread you've subscribed to has been posted in or something like that. I think it'd boost blog participation and cut down on posts.