For those who track calories, what specific apps or planners do you use and why?

Absolutely the best food diary I've ever used. I've been fighting the battle of the bulge all my life and tried them all. It has a more complete database of foods than all the others combined. It even lists popular restaurants and then their menu items. You don't have to waste time inputting calories and other nutritional values.

I used it for a year so I could get used to eating enough to accommodate my training. It's a great tool.