Originally posted by Sailguy
Driving to Redwood City for a dentist appointment. Then believe me, driving home, changing, then biking into work. So it will make me quite late, at least I'll be riding. 
I'm not sure if it'd work in all circumstances, but I've found that making such stops can be easily accomplished if you ride from the location of the errand -- the dentists' office in your case. The trick is remembering that you left your car somewhere unusual.