a subscribe option at the all blog posts page would be nice to subscribe/unsubscribe to all blog posts and
also a separate subscribe option at each blogs' list of posts to subscribe/unsubscribe for that one

regarding the subscribe/unsubscribe for all, I'd expect the way you do it to be similar to how you subscribe to forum boards (that is if functionality is missing at all forum boards page to subscribe/unsubscribe for all it should be added)

btw, maybe a central e-mail notifications page is needed (not sure if you've added one) accessible from one's profile

also, at the end of each blog post, I'd expect one to see option to subscribe/unsubscribe to/from the respective blog and at the end of the comments list an option to subscribe/unsubscribe to/from new user comments for this blog post (and when writing a new blog post you could see that option pre-checked for you and be able to clear it before posting the article or even later on)

maybe to implement the above some widget is needed to show a register-for-notification (subscription) option, taking as parameter a notifications-source context or something (not sure if notification-registration-point(s)-declaration is implemented in generic way now for the WebParts)

the way notifications are delivered could possibly be selected by the user in their profile settings, e.g. via monox message, via e-mail, or both (Facebook has similar thing if I remember well, to select if you want to see e-mail and/or notification in its UI)