This is a plot of the dates and arrival times of all the e-mail to my main e-mail address since I started work at the University. This is post-filtering, so most automatically-generated mail and spam has been filtered out; what is left is the automatic status messages that I was still willing to see, and my real mail.
The large horizontal dark band shows that I get most of my mail during working hours. The regular vertical light lines show that I get less mail on the weekends; timed reports show up as horizontal lines; timed jobs (which may run longer or shorter) show up as wiggly horizontal lines. A couple daily jobs at around 1am and 2am, which I began receiving reports on in about September 2002, can be seen to be taking longer over time. Another report came out at like clockwork at 5am. Apparently I began discarding it in December 2002.
Also, a systems incident on about Feb 12 2002 which had people running a cleanup script that reported its status by sending mail to the group, plus people discussing the incident itself, produces a notable vertical line on that day.
If you squint, you can seven get a slight sense of the amount of mail slowdown during the summer months and during breaks; there are dim white vertical areas at Christmas, for instance.
I have plans for a future version of this graph which will display message counts over 10-minute periods, using graylevels, perhaps grayscaled logarithmically. Another idea would be to aggregate the data by day of week, to quantify the weekend traffic falloff.
I have to say, this is probably the second-geekiest page on this website after the self-reproducing Perl script.