Where does the time go? Whether you need to know for billing purposes or just want a better idea of how your work day is split up, you can always answer that question with a good time-tracking application.
I use Ubuntu Linux and I've been using Hamster (http://projecthamster.wordpress.com/) for a couple of weeks now. It sits in a panel on the top of my screen. My favorite feature is that it unobtrusively notifies me every so often about what it thinks I'm doing (i.e. what I told it I'm doing). Now I just need to discipline myself to take 5 seconds and give it accurate information whenever it notifies me.