The January, 2010, Consumer Reports Magazine has a list of everyday annoyances that really get under the skin of folks like you and me. Of the 20 listed, 5 are directly related to driving and traffic. I can identify!
On a scale of 1 to 10, with 10 being the most annoying:
Cell-phone use by drivers 8.0
Very slow drivers 7.0
Traffic jams 6.9
Speeding drivers 6.1
All but cell-phone use can be mostly mitigated by switching to bike transportation. In fact they are a list of reasons that partially compelled me to make the switch.