I used to get really frustrated with the stop-and-start nature of my commute from the suburbs into downtown Boston. then I read a bit about interval training and helped put my mind at ease.

now I push as hard as I can until an interruption, and then getting going as soon as I can after the light changes / traffic gets out of my way. call it a poor man's interval training.

I tend to use the commute to work this way, and then take a slower, more leisurely route on the way home. this keeps my heart rate more in the so-called "fat-burning zone". I don't have any idea whether this actually makes a difference, but given that I'm tired at the end of the day and don't want to deal with the hills, it works for me.