Slife
Slife is a tool to automatically track your computer usage. You just need to create an account and download the open-source Slife client. Once ready, the tool will record the time that you spend on applications and web pages. You can visit the web page to see visualizations of your computer activities. One view allows you to see how much time you've spent per application. You can also create categories of your activities (e.g., reading news, doing research) and assign applications and documents to these categories. You can see visualizations of the categories in pie charts.