Kapow - Kapow is a punch clock program designed to easily keep track of your hours, whether you're...
TopTracker - Beautiful, free time tracking
Kimai - Kimai is a free open source timetracker.
timeBuzzer - timeBuzzer enables freelancers and project-driven teams to track their time at the touch of a button, understand where their time goes and create reports with just a few clicks.
Personal Task Manager - PTM is an Open Source time tracking tool hosted by Sourceforge.net.
Cattr - Cattr is a free open-source self-hosted time tracker with desktop clients for windows, mac, linux.