Joachim Breitner's Homepage
The Automatic Rule Based Time Tracker that I have created some weeks ago is now available in Debian unstable, so if if you were reluctant to use it because you did not want to figure out how to compile the Haskell code, you can just do apt-get install arbtt.
Although it’s such a young project, it already has a fork: Andreas Klöckner was very impatient with a feature request (sensible merging of logs from different hosts), so we went ahead and re-implemented arbtt in python, named whatup. Although I prefer contributions to arbtt, it shows that the principle of arbtt is useful. And I won’t be shy to copy nice ideas from him, as well :-)