You might sometimes need a stopwatch to time some operation in the GUI or your program. Easy Stopwatch is a simple application for Ubuntu that can be used for this.
It is available in the Ubuntu repositories, so installation is easy:
$ sudo apt-get install easy-stopwatch
Run it from the Dash as Easy Stopwatch. In addition to start-stop times, it also supports collecting lap times. This can be useful to collect times of repeating tasks. Open the Lap sidebar and press the Lap button on completion of every lap or event.
Tried with: Easy Stopwatch 12.08.3 and Ubuntu 12.04 LTS