Every once in a great while I will get the feeling that I am the most productive coder on the planet. Then I remember Carmack's .plan files and am humbled.
Edit: Actually, they were easier to find than I thought:
Here's an example of a project log for a current project I'm working on: http://www.labradoc.com/i/follower/p/notes-qualcomm-apq8060-...
My style is more verbose than Carmack's but Labradoc can be used with either approach.