One thing I have discovered at work is how pleasant it is to have a monitor devoted exclusively to email. For me, email has become the central clearinghouse for virtually all information and action items. To remind myself of something, I send an email from my phone. I also track emails by applying ‘@Pending’ and ‘@Waiting For’ labels to them. Email can also be searched instantly, unlike having to search separately through blog posts, comments, wiki entries, document files, etc.
Having a second monitor exclusively for email is qualitatively different from having a window open, or even having a second desktop devoted to email use. This is because it is glanceable – you can check almost instantly and with minimal distraction whether anything new has come up. It is also easy to shift information from one screen to another: making reference to a document or website in a message, or adding information from an email to a website, calendar, etc. With a dedicated monitor, email never gets buried or left unnoticed for too long.
Much as I appreciate the 24″ screen on my iMac, I suspect I will eventually go for a two-monitor setup at home. Arguably, such a setup is a mark of excess. That being said, when your entire life is coordinated through computers, it is perhaps an acceptable area in which to devote resources (including a share of your direct and embedded greenhouse gas emissions).