Open source Timekeeping software

sujit writes: Can the slashdot community throw some light on some simple and open source web-based timekeeping software that allows employees to keep track of their Shifts, apply for time-offs, and other features that would be useful? I've looked for some modules and plugins that could be added to Joomla or Mambo or Drupal but came up with nothing. I wouldn't mind writing one from scratch, but I'd like to find out if there's anything available on the internet that I could use.