To find out how much your body needs of a certain nutrient, you can check out the Daily Values or the more detailed DRIs for Energy, Macronutrients, Vitamins and Minerals. These are all just reference points, so don't get too caught up in the numbers!
The Nutrient Information section will give you more information about the various nutrients. You will find information about the Macronutrients, Vitamins, Minerals, Fatty Acids and Omega-3, 6 and 9. You can find good food sources for these nutrients on the Good Sources pages.
For more information about the nutrients that can be found in a particular food, you can check out the Nutrient Content Tables. If you read the Introduction to these tables, you will understand the meaning behind the percentages and the color coding.
Don't forget to visit the Food Dictionary, which contains definitions of food products. Behind many of these definitions, you'll find direct links to the nutrient information and pictures of these food items. The collection of pictures can be found at this link.
Even includes a measurement counter and converter
Check out VeganPeace's great source of nutrient information