RescueTime

RescueTime is a cool service for logging time usage from active desktop windows. They have a nice web dashboard for analysis and goal setting. The possibilities to extend the idea of logging human activity are limitless: smartphones, entertainment systems, even sleep time. I really hope that RescueTime (or any similar service) gets popular.

Why do I recommend RescueTime is simply because I have experience on these applications. A few years ago I implemented a similar system for personal use and before that I used only Excel for time management. I still need Excel for project planning. But for automatic logging you can't find a better solution than RescueTime right now.