Boyd Johnson has an ingenious way of tracking his time throughout the day. Just open Windows Notepad and, when starting a task, hit F5, which stamps the time into your text file. Make a note to help you flesh out the task on your billing sheet later, and off you go. Whenever you switch tasks, hit F5 in Notepad again.
I use three text editors in Linux: Gedit, Scribes, and Bluefish, but none of them have this handy feature, unfortunately. gtimelog does the same thing in a nice package, however.
Capturing More Time…And Keeping Your Clients Happy While Doing It [ABA Law Practice Today]