Is it good to stretch the muscles one is exercising between weight lifting series? For example, if I am doing bench presses, should I stretch my chest and arms muscles in between one series and the next?
Well, if you are doing strength workout don't stretch between the series. Only after you have done the whole workout. That is done in order to keep your muscles tight and in that way you get a little more strength.
However, if you are doing mass it's very good to stretch. I have answered this kind of question here: [question] when to stretch to help building muscle?.