This is a question that is often brought up. If I have to give a definitive answer, I would clearly say no, however, if you and are your spouse are getting an amicable divorce, meaning that you have already signed the divorce agreement, then it is probably okay to date, however, you should not spend money on your new boyfriend/girlfriend until the divorce is final.
If you are in a nasty divorce, it is best not to date someone new until your divorce is final. Your spouse is going to try to use everything he or she has against you to make you look bad in front of the judge.
If you are seeking alimony, you definitely should not date anyone. It will affect the judge's decision on whether you should be awarded alimony. The law assumes that if you have moved on to another relationship, you will not need support from your future ex.
If you are litigating custody, it is best not date someone until your divorce is final. You should think about your children, how they are already adapting to the trauma of their parents no longer living together, and to introduce someone new could be very confusing for them.