Today I installed the latest version of GnoTime (previously Gnome Time Tracker). I have been using GTT/GnoTime for years but have only had old copies.
The new version (2.1.5) is the answer to all the things I wanted while using the old version.
While I have been stuck in the windows world the GTT developers have been busy making the developers life a little easier.
The new version includes subprojects, diary entries, export, journals and idle detection. Perfect for keeping track of billable or project time.
Find it at http://gttr.sourceforge.net/