Vegetables are packed full of vitamins, minerals, and phytochemicals.  However, alot of the plant foods Eagl listed were high calorie.  Carrots are tubers, basically a large carbohydrate source.  Beans are legumes, chocked full of complex carbs and protein.  Both tubers and legumes are high energy foods.
'Real' vegetables are low in energy.  These include : Broccoli, cauliflower, lettuce, spinach, khale, asparagus, brussel sprouts, cuccumbers, etc.  
I've toyed around with creating a diet of my own.  The best diet I can create would be based around vegetables, with lean meats and healthy sources of fat, along with a few servings of fruit.  But the vegetables are the key.