Dan Ariely has a good post about why our current "productivity tools" generate time-wasting or addictive behavior: he looks to B. F. Skinner's work on "schedules of reinforcement" that found that random rewards inspired more work than predictable rewards. (It got more work out of rats, anyway. Come to think of it, it also works for graduate students.)

Ariely comments that Skinner's work

gives me a better understanding of my own e-mail addiction, and more important, it might suggest a few means of escape from this Skinner box and its variable schedule of reinforcement. One helpful approach I’ve discovered is to turn off the automatic e-mail-checking feature. This action doesn’t eliminate my checking email too often, but it reduces the frequency with which my computer notifies me that I have new e-mail waiting (some of it, I would think to myself, must be interesting, urgent, or relevant). Another way I am trying to wean myself from continuously checking email (a tendency that only got worse for me when I got an iPhone), is by only checking email during specific blocks of time. If we understand the hold that a random schedule of reinforcement has on our email behavior, maybe, just maybe we can outsmart our own nature.

There's also this observation of Skinner's own work habits.

Skinner had a trick to counterbalance daily distractions: As soon as he arrived at his office, he would write 800 words on whatever research project he happened to be working on—and he did this before doing anything else. Granted, 800 words is not a lot in the scheme of things but if you think about writing 800 words each day you would realize how this small output can add up over time.

This is something I try to do, but I'm also aware that I need to be more disciplined about it. There aren't THAT many e-mails waiting for me in the morning that require my immediate attention, and I suspect that I'm actually more likely to lose track of tasks or not reply to a message if I read it, think to myself "I'll deal with this later," then set it aside. For me, the in-box is not nearly as effective a place to stack tasks than, say, a physical pile (or even better, a written list in my little Moleskine notebook).