A couple of good articles regarding the art of managing email. [via: Jonathan Hardwick: Shipping Version One]
Potentially the best line is in the first article and has to be:
One CEO I've worked with charges staff members five dollars from their budget for each e-mail she receives. Amazingly, her overload has gone down, the relevance of e-mails has gone up, and the senders are happy, too, because the added thought often results in them solving more problems on their own.