Calorie Counters and Diet Software

Mobile Diet Trackers for Palm OS, Pocket PC, or Symbian OS

Weight-By-Date Mobile (Palm OS, Pocket PC)
Top pick.

HealthFitCounter (Dedicated, Palm OS, Pocket PC)
Diet and exercise tracker (formerly called NutriCounter). NOTE: You do not need a PDA for this - it is a dedicated handheld calorie counter.

Calorie King Diet Diary (Palm OS)
Also have a Food Database for pocket PC.

DietManager (Pocket PC)
Tracks diet and exercise. Small food database.

Mobi-Systems Diets 4 (Palm OS)
Tracks calories, carbs, and proteins. 4,500 item food database (including fast food).

RMRDiet (Pocket PC, Symbian, Palm)
Diet and exercise tracker. 6000 item food database.

Coheso CalorieSmart (Dedicated device)
Handheld electronic calorie counter and Food Diary. Over 35000 food items, and information from 250 restaurants.

Mobile Phone Apps

Diet Organizer
Calorie counter for non iPhone mobiles.

SparkPeople
Several free apps for all kinds of devices including the iPhone.

Get Jar
Many dieting apps to choose from.

Official iPhone Fitness Apps