I've used fitday for over a year now, so I have a record of EVERYTHING I've eaten since last September. Fitday lets you look at vitamins and minerals, as well as carbs/fat/protien, and track excercise etc, and then you can do a little bar graph pof eaten vs. burned. I prefer the free version since I can get to it online anywhere instead of having it downloaded on my computer.
As I also weigh everything I can, it's made me very good at knowing what a portion is when I eat out. Without it I would have a hard time keeping macronutrients balanced.