Keeper of Time
tracks down the time you are spending on tasks and projects. It allows you to define Projects and assign tasks to them. A task stores information like the time you used already - a timer assists you and raises your work time on a minute based scheme. You can leave notes for each task and declare tasks and projects as finished.
Keeper of Time is based on an application I have written for my personal time keeping some time ago, this public beta version is freely available. KoT will probably not be free in its final release, the price will be in the $10 range.