I found this new book on managing email today, called The Hamster Revolution, co-authored by the guy behind the One Minute Manager and a co-author of Who Moved My Cheese?
Now I'm a little biased because I'm not a real fan of the Who Moved My Cheese? style, but there are still some good ideas in this book. Probably the best is their COTA (Clients, Outputs, Team and Administration) model that provides a folder scheme and prioritisation method for filing email (and other documents).
However, the Who Moved My Cheese style makes it very simplistic and I think the main criticism I have while flicking through this book is that it doesn't appear to address what I consider to be one of the fundamental issues of information overload, selecting and using the right communication tool for the job. However, it does at least take you through a process of looking at how well your team uses email, which is another issue I consider important.