Recently I felt the need to have some kind of time tracking tool, so I wrote a simple one in ruby. It requires only two gems to work (‘rubygems’ and ‘sqlite3-ruby’).
It is definitely a work in progress, but right now it is very easy to use and it gives reports for the last few days, last 3 weeks, and current month. Also, for mac users, it has the option to change your Adium statuses using osascript, with customizable status messages for a few situations.
weekly report
monthly report
You can find the source code and installation instructions at github (http://github.com/jao/termite).
I plan to add features like, defining projects and tags to the worked time, and exporting the reports to formats like pdf and csv.