Are you chronically late? Productivity blog ZenHabits suggests getting in the habit of overestimating:
Make a conscious effort to start getting ready earlier, and to leave earlier. This also makes driving less stressful. Time yourself to see how long it actually takes to get ready, and how long it actually takes to get somewhere. You've probably been underestimating these times. Once you know these times, you can plan backwards so that you show up 10 minutes early each time. It's a good feeling.
A good habit to get into, that's for sure. Have you conquered the lateness monkey? Let's hear how in the comments.