With the growth of social media email notifications (from facebook, twitter, asw, etc...) I wake up every morning to about 40 emails. A method to filter these into groups - event type emails which include fb, twitter and broadcast emails versus personal emails would make my life so much easier and my email a lot less cluttered.
Another way to improve email is to find a way to deal with unread emails- so you need some sort of 'interim' board where you can drop emails you want to deal with later on.
Obviously these are only a couple of ways that email could become a better and more efficient tool...I am certain there is scope for more suggestions.