I hope you're kidding! Keeping a bunch of pissed off soon-to-be-ex-employees around the workplace isn't good for anyone. The best you can do is to lay people off on Friday morning so at least they can be with your friends and family over the weekend for support.
I think early in the week is the best way - at least when firing people. If you let someone go on Monday or Tuesday they can immediately start looking for a new job the next morning. With any luck maybe they can start getting callbacks or a phone interview before the end of the week. That goes a long way toward boosting morale. The weekend makes it a little more difficult. Sure, they can update their resumes, apply online, etc., but that kind of ruins the weekend and leaves a lot of time to start feeling hopeless or really pissed off.
Plus, some people might not mind so much if you tell them first thing Monday morning that they have to go home. :)
