Timeous is a simple and effective time-tracking app for Mac OS 10.4 or later. It allows you to track time on multiple projects ("tabs") and set independent hourly rates and tax percentages. Each time you start the Timeous timer, an entry is created in your current project tab. These entries are then sorted by day and time. When you stop the timer, you will see the total time of that chunk of work, and you can add notes to the entry to explain what work was performed.

Data is automatically saved, and the program's status bar shows the total time and cost associated with the project. You can export the time entries to a text file (useful for providing to a client when you send them an invoice). Timeous is a free download and a Universal binary.