This site, www.nutritiondata.com, is without a doubt the most thorough, extensive, no-frills, no-nonsense, educational and useful websites I’ve ever seen.
The articles on weightloss are actually based on the energy equation, and it also explains harder concepts like glycemic indexes.
There is also information on most every type of food you can imagine, a complete nutritional breakdown. The coolest feature is their “Pantry” where you can store foods you eat often, and track your diet throughout the day and give you a thorough daily analysis. Great for tracking calories, macronutrients, and vitamins.
I’ve used it for about a month to stay below 2000 calories a day, and those extra pounds are quickly disappearing. Best of all, it’s fun! And it takes all the guesswork out of losing weight, and eating healthy.