Creddon - Tweet for a cause and a sponsor will donate $1 to charity
MyFitnessPal - Track the number of calories that you consume each day with MyFitnessPal. The app also lets you create a diet and track the exercise that you complete each day whether it's walking, running or some other type of program.
All or Nothing - Competitive donations for causes you care about.
Lose it! - Snap a photo of your food to get nutritional facts
Public Design Vault - 500+ design tools for public good, all in one place
Noom - Get life-long weight-loss results