I am using a very simple system for remembering commands and procedures, and for tracking what I work on. I have two plain text files called notes.txt and worktime.txt. In the notes file, I write down things that are important to remember. For example: various shell commands, steps when creating a new release, how to install and configure tools, company procedures for time reporting etc.
In the worktime file, I write down the hours I worked that day, and what I worked on. I also have a python script that calculates the number of hours worked for the day and the week.
Henrik Warne's blog 