Jake of the Web

www.diettelevision.com
An attractively designed, very thorough weight-loss site with three main sections:

-Learn It
Diet Finder
Gives you fader bars to select the priority of various aspects of dieting:
How often you want to eat certain types of foods - meat, veggies, dairy, etc.
How important it is to you to lose weight quickly, want to feel better and healthier
How important it is to you to have frequent meals
How often you want to be able to dine out
Affordability

Based on the choices you set, it ranks the top 20 diet types for you over on the side.

Exercise finder
Enter your current weight and weight goal, then what types of exercises sound fun to you.
How long you want your workout to be, how many times a week you think you can work out, and how many calories you want to cut out of your diet per week.
Based on that, it will give you an approximate length of time before you reach your weight goal.
It then gives you examples of some simple exercises based on what you entered

-Lose It
It then gives you tools to track your progress, including weight lost/gained, how much water you drink daily, how much sleep you get, and your mood from day to day.
You can track what meals you have had, and even enter your daily meal from your cell phone.

-Link up
Also has a social networking portion, where you can meet other people, see what works for them, get inspired and inspire other people.
You can use as few or as many of these aspects as you want.