If you're like me, you want to know how much time you're actually spending on projects. I've been using a very useful applet for Gnome desktop called Hamster. With Hamster, I'm able to start and stop time tracking on a particular task, enter previous times, and see time charts for days, weeks, and months. Here's a quick screen shot.

To install Hamster in Ubuntu you can either search for "hamster-applet" in Synaptic or use apt-get.

sudo apt-get install hamster-applet

Otherwise, check out Hamster documentation. Once you've installed it, right click on your menu and select "Add to Panel". In the "Add to Panel" window select "Time Tracker". Enjoy.