Firefox extension Timelope

All platforms with Firefox: Firefox extension Timelope helps you keep track of web sites you've visited, when you've visited them, and how long you spent on each site. Sign up for an account, install the extension, authorize yourself, and you're ready to roll. Timelope works in the background and keeps track of the number of pages you visit: as you visit more pages, the number of Timelope "hops" is increased. Additionally, Timelope features a separate but useful social networking function where you can follow friends and see exactly where they've been online. By default, your visited web sites are private; you can make your stream public if you are interested in the social features of Timelope. For a similar application that keeps track of all computer-related activities to improve productivity, is free, works wherever Firefox does.