Got_To_Do_It, I weight every day, too. I have NOT noticed any pattern, except things just like Ranae said (saltiness in foods, extra weight-training, extra cardio, etc.).
BUT, I only write down my weight loss in my own book once/month along with measurements. ONLY BECAUSE of the Sunday weigh-in, do I post weekly. AND, I've been surprised that I've lost ANYTHING for the weekly weigh-ins! I can go a long time without losing, and then WHAM.