If you have read Dr. Atkins' New Diet Revolution by Robert C. Atkins, MD and are following Atkins lowcarb diet, than you know they recommend weighing yourself once a week.  I do think that weighing once a week can help you stay motivated because than you don't see how much your weight fluctuates from a day to day basis.  I've tried to weigh once a week and I've also tried weighing daily.  I find for myself that weighing daily helps keep me more accountable to the food that I put into my body.  I tend to eat better when I weigh daily than when I weigh once a week.

I remember when I attempted Weight Watchers, which is a great weight loss program, that I weighed in once a week at their facility.  It works for some people, but it didn't work for me.  I would find that I would eat pretty well and than about 2 days before my weigh in I would eat even less to try and tweak the scale for my emotional gain.  I would always lose weight, but than the day after my weigh in I would usually eat pretty bad.  It didn't work for me because I didn't feel like I was following the program properly.  That's why I love eating lowcarb.  I don't feel like I have to have "cheat days" because I love what I'm eating and I don't have to starve myself to lose weight.  Something my mom always told me, while I would go from diet to diet throughout my life, is to find a diet I can stick to and do it.  Consistency is the key to your ultimate weight loss.  Find a program that works best for you and stick to it and you will succeed.